Hopefully, by the time you are there, Disney will have more of their "bugs" worked out. We were in parks for five days, and never knew what we were going to get with
MDE.
-The first day, we could not make any changes on our iPhone MDE app. Never used a kiosk that day. (Epcot)
-The second day, we could easily make changes on MDE, & visited a FP+ kiosk to keep adding. Unfiortunately, we discovered that at the end of the night, it would not let us cancel the unused Fantasmic FP+ that we were not going to use.
- The third day, we did not have any problems with MDE.
- The fourth day, MDE app would allow changes, but it was loading incorrectly pretty regularly. This error was also occurring at the FP+ kiosks, and guests would have to scan their tickets/magicbands more than once, so the system would pull up all of the names and attractions associated with the card. Super annoying and made the lines move extra slow.
- The fifth day morning was he!! . . . Seriously! Both the MDE app and the kiosks were a mess, and the CMs were as frustrated as everyone else. The names of the attractions kept showing up as "unknown", availability would disappear, and windows of time would reflect 10 minutes instead of an hour. You could tell a glitch had occurred, because during mid-afternoon many of th FP+ lines were longer than the stand-by lines, and the CMs were trying to direct people to go stand-by, explaining it would actually be faster than FP+.
There were tons of Disney CMs around surveying guests on their experiences. Hopefully, they collected some constructive FP+ comments.