The thing I struggle with is would you seriously play PC games under a TV, steamed form your actual gaming PC with out a mouse and keyboard? Onlive tried it and failed miserably although i loved the idea (i bought one *sigh*) they had it just doesn't really work in the real world.Do work?
As for "go online" and a media center, it will probably have that as well.

That is why the Steam client is getting all the features as well. The OS is for peeps who want to play games in their living room on a well powerful machine or even a barebones/micro PC to stream games and media.
