I'm having the exact same problem and it made me lose a lot of time. I tried using opacity to show/hide the view that I wanted to animate and it worked until I tried to "navigate" to another view and the UI got unresponsive. There is a loop and a possible memory leak happening. It seems I will need to use the timer trick for now.

After analyzing almost line by line the real time game sample given by Apple, I found one little difference, I didn't have the Group Activities entitlement. After adding this, the multiplayer game started working again. Probably this was not a requirement in previous versions, I don't know, but problem solved. I supposed Apple could give a better error message, though.