I have been meaning to come back here and write a more complete report of my experience with SDFP and someone was asking about it in my dining report.... so I read back several pages and have a bunch of thoughts based on questions I had before my trip and things I wasn't sure about, so hopefully this will help someone else.
First of all, I'm a single mom and I was traveling alone with my 8 year old son. I would imagine if you have a big family with people who want to ride different things it would get a lot more complicated but since it was just us and if he didn't want to ride it, I didn't ride it and if he did we did... it made it a lot more simple than people who deal with kid swap and split parties and fp+ on a few bands and not all in your party etc.
Obtaining media:
I'm a DVC member and we did a 3-way split stay so I was entitled to 6 magic bands total. I declined 2 sets and added two phantoms (no cost for DVC) to my single night reservation and when the bands arrived, I modified my reservation to remove the phantoms. These were of course unlinked to tickets.
I did get one set of bands for our primary account as backups to our purchased bands and I carried them in the backpack the whole time... I had a Dooney & Bourke band that I could have linked to a phantom but I wanted it to be my primary and kiddo had a BB8-band with the same deal, so I linked them to my primary... so we wore our decorator bands, I kept a set of backup (free from WDW, clones of our primary) bands in the backpack and we had our secondary bands in different colors from the primary bands. We went in early december so I also bought magic band wraps decorated in christmas and we wore a band on each wrist. I highly recommend having a backup clone band if you can manage it as the kiddo lost his precious bb8 band on our last day on space mountain and having the backup band allowed us to continue our day with zero interruption.
I also used a third set of SDFP (more on that later) and I asked my ex-inlaws for their ticket media (not magic bands) that I kept in my pocket all the time. Their MDE was not linked with my MDE so they were in some ways the most simple to use. Honestly if you think you might get confused with more than one set of bands, using cards worked really well and it was really easy to keep track of what was on what using the different media.
I will say that if you feel like it is less than honest to put phantoms in your room in order to obtain free bands (I didn't feel bad about it because I 1) had spent $75 on vanity bands and just wanted them linked a certain way and 2) declined a bunch more free bands we were entitled to anyway) that it is REALLY worth it to just pay the $12.99 for an extra unlinked magic band. Think of it this way... if you have a 4 day ticket, it's a less than $4 per day per person to be able to use SDFP and I would say that it is MORE than worth the little extra expense. If you can obtain freebies, great, but after using SDFP I would totally pay for bands if I had to.
Using SDFP in the parks:
First off I'd say that generally FP+ availability is pretty good in the morning. If you do RD at a park, it might be worth it to swing by a kiosk first and pick up some extra FP before heading to the line. I found this out when we went to RD at Epcot planning to go to test track first then soarin after. It turned out TT was closed so we ended up lining up on the Soarin' side and I was so discombobulated, I ended up hitting the FP+ kiosk first. There was a ton of availability for both TT and Soarin' starting as early as a 9am window that I ended up grabbing a FP+ for Soarin' from 9-10 and TT from 9:30-10:30 hoping that TT would be back up for 10:30 but figuring I could at least get a paper anytime FP from them if it still wasn't up yet that I could use later. So after that off we went to use our 9am Soarin' FP+ and there was still only a posted 15 minute (which was more like 10 and included all of the walk time and then waiting at the appropriate concourse to get onto the ride) wait so we walked on once, then went back out and used our FP+ when the wait was a bit higher... we rode it twice in a row and then livin' with the land, which I had booked on my primary bands for 9:15-10:15 when I did my FP+ 60 days out.
Also I would say that FP+ availability at the kiosks changes on an almost second to second basis. Honestly if you don't see what you are looking for refresh, refresh again, maybe exit out and walk down to a different kiosk to kill a minute or two and refresh again. People seem to be constantly dropping things and making changes and you never know what you will find. Just because you don't see something available doesn't mean it won't be available later in the day.
Also some people have concerns about CMs being overly "helpful" when you're trying to mess with your SDFP - I found a firm but polite "No thank you, I've got it" prevented them from getting all up in my stuff. In fact, the only time I had remotely an issue was when another guest was virtually crawling up my butt waiting for me to finish and I was trying to figure out how to nest FP+ and she was really agitating me. There were more kiosks open so I just ended my transaction and moved to another one. I don't know if she had some kind of OCD and HAD to use that kiosk or something but it was not worth arguing over.. I asked her to please give me space once and she stepped back but ended up right back up my butt so I just moved. I always tried to go to a kiosks where there were relatively few people around too, when they are all lined up people seem to cluster at the ones closest to the inlet of the major flow of traffic.
Also about using 2 sets of SDFP (for a total of 3 sets of FP) vs. 1 set of SDFP - I read back and saw various opinions on this but I will say that in general, having the third set was VERY VERY useful. I did NOT walk around with 9 FP+ planned at any given time, but what it did allow me to do was hold multiple tier 1 FP per day (I had FEA on my primary, Soarin' on my second and TT on my third at one point). What it also allowed me to do was to overlap times more efficiently which really was a HUGE benefit to reducing extra walking and waiting time, especially in Epcot and in the MK. So while I will say that holding 9 FP at any given time is probably a bit overboard there were times when I held something like 7 and having the ability to put something on the cards really made our touring much better and more efficient at times.
Now I will go park by park and talk about my experiences with SDFP:
Animal Kingdom
This was our first park day and unless you want to ride things multiple times, this is probably the park where SDFP is least useful. I did practice using the bands here while there was no pressure but we did EMH and went straight to dinoland where we rode dinosaur and primeval whirl multiple times (it was hurl-tastic, I had to call uncle after the 3rd of 4th ride... my kid loves both of those rides very much). My son won't ride everest (we rode it last time and he hated it) and it was December so I was not into Kali river rapids. My prebooked FP+ were the safari, festival of the lion king and something else I can't even remember at this point... maybe tough to be a bug. Really only the safari required it. I think if you wanted to do the safari twice in one day - maybe one early and one at dusk, the SDFP could be useful as there was lots of safari availability later in the day. Also with RoL i'm sure having some extra FP capacity might be useful. But we did not use it at all except for practice. The one thing I DID successfully do was pick up a perfectly timed toy story midway mania FP+ just as we scanned through at the safari (it was our last FP+) since we were planning to be at HS that evening for the Jingle Bell Jingle Bam dessert party... so that's what I mean, keep checking because good stuff pops up all the time. I was actually looking for great movie ride and that one popped up instead.
Hollywood Studios
This is probably the second least useful park (for us) because my kid won't do RnR and would have gone on ToT for me, but only under duress so we ended up not doing it. We did the Jedi Training academy thing and they were giving out paper FP+ for your time in line at RD, good for anything but TSMM but as it turned out we didn't even use it for anything. I think for folks who like RnR and ToT it's GREAT because there was a ton of availability for both throughout the day. For us, the waits were not long enough for anything to need it except for TSMM, which I either booked at 60 days or got lucky on using the app on my phone.
Epcot
I hit the kiosks at the entry to either side of future world many times... they were very convenient for checking what was available at any given time and because of that we ended up riding Soarin' 5 times and TT 3 or 4 times in 1.5 days.
As I mentioned above, I found having 2 sets of FP+ very very useful here... both for holding extra Tier 1 FPs and also for more efficiently stacking my FP+ together. I know you can have them start in back to back windows but for many times and much of my plans, it was easier to have certain things in the same window - So I was able to have the seas with nemo and turtle talk with crush at the same time, Figment and the Land during the same 1 hour period, etc. We never used it for Illuminations viewing though, because every time I checked I was able to pick up a great other Soarin' FP+ and we ended up doing that ride 5x in our trip. It was truly awesome but I will say that when you can keep picking up the major rides, it does make the minor rides a bit harder to fit in and I did feel like the pace of our trip was faster than before.
MK
I have read that there are kiosks at city hall but there was such a HUGE line I could not get near the place there was such a huge line and I didn't see a way to get inside without standing in the line and I didn't see any outside, so we ended up using the ones in tomorrowland. They were the most convenient to hit right when coming in the park as you make the hard right into tomorrowland before hitting the castle and you are right there. I think I used the ones in adventureland a couple of times as well but for the most part, with the use of 2 extra bands and being able to make a 4th FP+ on the app, I didn't have to hit them more than once so once on the way in was sufficient most of the time.
MK was, as many others have pointed out, by far the most useful park to have SDFP in because there are so many SDFP available. I never saw 7DMT available and the mountains were often gone too and Jungle cruise seemed to go next (maybe it's having a renaissance or maybe it's the jingle cruise overlay?) but on less busy days availability was good on most other things. Having 3 sets of FP+ allowed me to do things like (these times are just for example) Space Mountain from 1-2, Buzz from 1:15-2:15, Tomorrowland speedway from 1:30-2:30... or another good trio was Pirates/Jungle Cruise/Magic Carpets... (fill in with Tiki room). Having the second set of SDFP just really helped me in nesting my FP either close together or right on top of each other so we were never waiting for windows to open and we were able to do whole sections of the park basically in the amount if time it takes to do those rides and walk from ride to ride.
On the night when they were PACKED, a wednesday NON party night, I won't lie - when we showed up around 7pm there were not many FP available... but upon refreshing a few times I was able to get tea cups, small world and Pooh on two cards in overlapping times in close proximity to 7DMT and Peter Pan that i had booked back to back ahead of time and it was so crowded all of these things had around 45 minute standby waits, so even though it was so packed, we could have made a nice evening out of fantasyland with our SDFP. Unfortunately it was SO crowded you could barely walk from ride to ride so we rode 7DMT, we rode Peter Pan and after the FP+ line for Peter Pan ended up being 25 minutes, both the kid and I decided we had had enough of an already very long day and went back to our room at the poly to watch the fireworks from there. It was glorious and did you know room service will deliver drinks from the Tambu lounge for the same price as the lounge +$3 service fee (and tip but I'd pay that in the lounge)? But I digress.
So what SDFP allowed me to do was to book our tippy top favorites multiple times in advance... 7DMT, Space Mountain, Splash Mountain, BTMRR and Peter Pan in advance and we were able to fill in everything else using SDFP on little to no wait. The only one that seemed harder to get than most was Jungle (jingle) cruise and Buzz seemed to go quickly too... but on less crowded days (meaning not completely packed wall to wall with people) there was at least some availability.
So in summary, I will say that SDFP REALLY enhanced the quality of our trip. My kiddo is on the spectrum and waiting is rough for him... we never had to wait for anything, except on a very long personalization line at the christmas shop at Disney Springs. Kid kept asking if we could FP it, spoiled! Keeping track of the bands was not difficult, I took photos to remind me what I had that did not show up on the app. To tell the kiddo which to scan I would just say "regular" "christmas" (we decorated our SDFP bands with christmas stuff) and "card" and he knew exactly what to scan where. The kid only scanned the wrong band once... it was at peter pan and the CM called out the name on his band and I just told him that the kiddo is "G" who scanned next, he accidentally scanned the wrong band. He didn't bat an eye at that and didn't seem to care as long as "J" which was the name on the other band didn't sneak in.
If there is any small downside, it is that our trip was more gogogo than our last trip was as we were able to go from ride to ride to ride with relatively little wait and knock out a whole land in like an hour. It did make getting to the secondary stuff a bit more of a chore but it was so exciting to get to ride Soarin' or TT or TSMM AGAIN that it was worth the tradeoff. I also think it really helped in efficiency as far as zig zagging both within a land/area but also from one area to the next. That was one thing I didn't do efficiently when I went in 2014 and I felt like we were more tired due to a lot of extra walking... I really tried to minimize my steps when we were going park open to park close and it helped. Using SDFP to be able to double and triple up on times for rides in close proximity really helped efficiency a lot. If your goal is to do lots of rides, it's definitely the way to go. Kiddo was in HEAVEN. It is just a real rush when you get ANOTHER Soarin' FP and it is your favorite ride and you might find yourself rushing to tier 2's like nemo because you were able to score another unplanned Soarin'.
That's about it I think. Sorry to be so long, but I figured my experience might be useful. Happy to answer any questions anyone has that is not covered in the first page about the basic mechanics of the thing.
and didn't even think of asking my husband to try when he went (which might have been an exercise in futility anyway). I should be at a park Friday so will try to remember then. 
