Juli Clover, MacRumors:
The new Apple TV works with third-party Bluetooth controllers, but because they are an optional accessory, they are not allowed to be the primary input method for a game. This requirement will force developers who want to build games around controller use to also include a touch or motion-based control scheme for use with the Apple TV remote.
This seems overly-limiting and short-sighted. There are plenty of iPhone apps that require extra hardware to be functional; without the companion tiny helicopter toy, the controller app on my iPhone would be useless. There are plenty of games for which motion-based controls work, but there are also plenty that will work better with a controller.