On a new iPad mini 2, version 10.4 hangs when pressing play or selecting a world. It also hangs when pressing the back button on the world select screen. I was searching for a resolution and came across this thread.

http://www.minecraftforum.net/forums/support/minecraft-pocket-edition-support/2386981-very-slow-startup-on-ipad-w-new-router

Where the person discovered turning off wifi made the load times instant. I tested this and I had the same result. With wifi off, the game moves past the play button and the world select instantly. Turning wifi back on causes it to hang for a minute+.