I got the chance to use the Magic Bands while in WDW for Marathon Weekend and I LOVED them! I went into this experience remembering that it was a test, and after hearing (admittedly I haven't read most of the MB threads) about some of the issues that people were experiencing, I didn't go in expecting much.
My cousin and I were lucky enough to have a flawless experience with the bands. I know that was not the same for many people traveling at the same time, but for us they were great! We used them to get on to Magical Express and then to get into our room. We stayed at Caribbean Beach and since that resort is pretty spread out I was worried that they wouldn't work to open our door and it would take forever to get fixed, but luckily that wasn't the case. The night we arrived I decided to see how last minute FP+'s would work so I went to the MK. On the bus ride over I got on the
MDE app and tried to get a FP for Peter Pan, Haunted Mansion, and Space Mountain. Since I was getting to the park about 1.5 hours before the park closed I was only able to really get 1 FP+ and it was for Space Mountain. I had no problems getting into the park with my MB and annual pass attached and went straight to Space Mountain where I tried FP+ for the first time and got the green light.
This pattern continued throughout the 4 days that we were there. One thing that I think OKW Lover commented on was that since I had the MB on and it was linked to my Annual Pass, I was constantly forgetting to ask about AP discounts. Then when I did remember or the CM asked me if I had one, I would have to take out the card. Thank goodness I remember to bring it to the park with me!
Hopefully more and more people will continue to have good experiences with it. I was skeptical at first about over planning and having to make FP+ reservations before I leave, but as a mom of a 4 year old I think it will be helpful. I know he will love the independence of being able to use his band to use his own FP+ and open the door. I like that I won't have to fiddle with a bunch of cards while trying to keep tabs on him!