The Channels Apple TV application is great, but would benefit from a TV guide list as the one that is included in the iOS application.
The feature that would make it great, would be to make the iOS app work as a remote. That is navigate on the iOS application TV guide, and when you find something that you like, you click on it, and it immediately changes to that channel on the Apple TV.
The iOS application would work as a second screen, to control the content being displayed on the Apple TV.