I want to start by saying that I really love Channels and have little complaints. 
That being said I’ve never been a fan of the “On Now” tab layout. I feel it would be better to have the category tabs along the left side of the screen (like in the Guide tab) rather than along the top immediately under the main menu. Not only would it make navigation easier (by not having to press the back/menu button twice to get back to the top menu), but would also make the UI a bit more consistent.
While I’m at it, I’ll go so far as to say that I would also love to see the DVR and Recordings tabs combined into one DVR tab with a similar menu along the left side for selecting between Up Next, Recent Recordings, Schedule, and Passes.
I know it’s a lot of work to change UI elements like this and that you guys have your reasons for laying it out the way you did, but just wanted to throw my 2 cents out there! Keep up the great work!