This is news to me. When looking at an iPad recently the guy in the Apple store told me that anything I bought on iTunes could be moved to a new device should I ever upgrade. So long as I have the same AppleId (email?)
What else is non-transferable? Books? Music? Apps? (Can iDevices do other things?)
It's transferable, but not necessarily by downloading again from Apple. You just back up your downloads and then you can transfer them from device to device.
Not that it makes any sense not to allow people to download stuff multiple times, especially when said stuff is DRM'd, but try reasoning with the movie studios.
It might get better in the future though. Music is now mostly DRM free and you can re-download directly from iTunes. That changed not that long ago. If the music industry can change there's hope for the movie industry as well.
You can redownload: music, apps, books, TV shows. Movies aren't in that list. Also, you might not be able to redownload something if it's been taken off the store.
What else is non-transferable? Books? Music? Apps? (Can iDevices do other things?)