I've now taken three trips with Magic Bands and FP+, and I love both. MB's for the fact that I can lock my wallet in the safe in my hotel room, and can enter the park(s) and make all food and merchandise purchases with a tap of my wrist (although to be honest - and I have no doubt that this was Disney's intent - when all you have to do is tap, as opposed to pulling out a credit card or cash, it doesn't "feel" like you are spending "real" money, which leads to significantly fewer second-thoughts at the payment counters).
And for my family, FP+'s work great. We hit the parks at rope drop and power through until noon, take a break in the afternoons and head back to the hotel pool, and then come back to the park in the evening and know that we have three guaranteed rides/parade/fireworks.
Conceptually, FP+'s work well at a place like WDW, where you have a very limited number of rides that are spread out over four different parks, so they also provide the opportunity to park hop (unlike DL/DCA, park hopping at WDW involves a heck of alot of pre-planning and a minimum 20-40 minute bus ride) and know that you will be able to ride (at least some of) what you want at the second park, even though you weren't there first thing in the morning to grab FP's (unlike DL/DCA, once the daily allotment of FP's was gone, they were gone - for some of the more popular rides, they were often gone by late morning or early afternoon).
Much of the consternation and teeth gnashing about FP+'s at WDW has been with respect to tiering, where you are only allowed to pick one headliner and then two lesser rides (for which you would never have needed FP's in the past - I'm looking at you, Captain EO). In a park like Epcot, you only have two headliners - Soarin' and Test Track - so tiering is a necessary evil in order to allow people a reasonable opportunity to hopefully ride one of them via FP, as opposed to those staying onsite with 60 day booking ability to book both, which would effectively shut everyone else out. Same story at Hollywood Studios, where you have TSMM, the Aerosmith coaster and ToT, or at Animal Kingdon, where you have Everest, the Safari and Kali River Rapids. At DL, I can't see tiering being necessary, because all of the headliners are within a 5 minute walk of each other.
Some on the WDW boards also get their backs up about the 60 day booking policy (30 day, if you're not staying onsite) for FP+'s. I'll give them that one - it seems ridiculous to have to figure out which park you want to be at, that far in advance. That being said, it's still less ridiculous than the "I hope you know what kind of food you'll be in the mood for 180 days from now" advanced dining reservation policy, because in most cases, if you don't book the more popular restaurants 6 months out, you're not getting in. In Disney's defence, I can see why they would want people to commit as far out as possible - my assumption is that once you have people committed with reservations (for food and/or rides), they are less likely to cancel their trip or decide at the last minute to spend the day offsite at Universal or Sea World.
All to say, Magic Bands are great and for some FP+ are great as well (although what makes them great at WDW, wouldn't necessarily apply at DL/DCA).
I'm thinking DLR would have to get their scheduling act together first and that doesn't seem likely lol 
