OP-RD is fantastic, especially if MK opens at 8. We were there Nov 30th-Dec 5th.
Nov 30th MK walked to Adventureland first, ghost town!
Dec 2nd, MK did TL, again,empty. Poor Stitch was lonely so we stopped 2 different times for pics.
Now, that week had VERY LOW crowds on the TP site, so there is that.

BUT RD is still an advantage.
We picked away at FL with FPs, avoiding it first thing, except for NFL, that we did after TL and had no waits.
I find it just amazing though, since others brought up Universal, the difference in a crowd 2 at MK and a crowd 2 at Universal!

I purchased EP, just incase since we were covering both parks in one day, and we only "needed" twice. Crazy. Gringotts was only a 15 min wait at 4ish. I'm guessing SDMT at that same time was a lot more.
Anyway, as others have stated, after 3 FPs, even on low crowds, we couldn't get anything worthy when it worked for us.
But, a plus is, if a ride goes down, you can use it anytime or ride something else. SDMT went down, but we still rode it just 2 hours later.
Also, Splash went down right after the riverboat, so technically we rode it, but they gave us a free FP, so we could ride from a list of rides.
Also, had FP for EE, but didn't need it, rode standby 2x. So we were able to change our Fps to KRR.
In the end, I think we'd love FP+, if they just made a few more changes. 3 initial picks just isn't enough with the crowds at Disney. IMHO
Don't get me started on the tiering, we didn't have a problem at HS, bcuz we have a son who was tall enuf for TOT, but I wasn't ready for that for him, so we could use child swap to cover those rides. But Epcot, we only got in TT since we didn't do RD that day. And, you could say, well without FP+ we may not have even got in TT...

There are good things...
Enjoy your trip!!