The app itself is great and if it worked well most of the time, it would have been extremely helpful. However, the many bugs made for a frustrating experience.
Fastpass and reservation management when it works, is a huge time saver. However, there are times when attempting to modify an existing fastpass or reservation cause the entire app to crash. During such times, you are unable to add any fastpass. There are times I had to resort to the website to fix a reservation or fastpass.
There a intermittent issues with searching for attractions, events and dining. I was in the park, wanting to find the nearest restaurant and I ended up having to ask around because the app returned nothing when I tried to filter by dining. These intermittent issues seem to be on the server level, because at this very moment, I am, trying to figure out what attractions to add to my agenda tomorrow, but neither my iPad or iPhone will report that any attractions exist.
Overall, this is a great app mired with significant show-stopping bugs.