Worked great!! Had a small issue when we checked in where they didn't know we already had bands and had others waiting for us. That was fixed fast and we were good to go. Only other issues had to do with tuning on the Bio Scanners, pretty sure they are way too tightly tuned right now, not a big deal as they quickly reset your biometrics and you move on.
Oh and I guess I had one weird issue with a fastpass, where I changed it to a later time the night before. The Cast member said I was 2 and a half hours late. I brought up the pass on my iphone and we were granted access, so once again a non-issue. We loved the bands: convenient, fast, changing or making new Fastpasses the day before or day of was a breeze. One day I actually had a Splash Mountain Fastpass+, but got to ride it with a short wait earlier in the day; Meanwhile, Haunted Mansion was a 35 minute wait, so I switched the Splash Fastpass+ for a HM FP+ and went right in, it was awesome. Another thing which I forgot to mention in my review, me and my wife got sick during our trip and spent a lot of time sleeping in, unusual for me at WDW, well one of those days we had all early morning FPs at AK. When we both got up, even though it was already passed our FP time, I was able to switch them from AK to MK which had late hours that day.
I thought only 3 Fastpasses was going to be an issue, but to be honest on most days I had trouble thinking what to use that 3rd FP on. FP+ also seemed to "flatten", by that I mean make the shorter, most of the lines that used to be really held up by Fastpass like Peter Pan, which used to be nothing but a steady stream of Fastpass followed by 1, maybe 2 families.
On a side note, what was with the Massive amounts of people in the parks these first 2 weeks of December? I've never seen it like this during this point of the year, been going around this time for most of the last 7 years now, wall to wall people, MVMCP sold out most nights, it was a mad house!!