Currently connected to the flatscreen TV in the living room: one cable box from Comcast, one Apple TV, one Wii and one Blu-Ray player with integrated Netflix subscription. We're not lacking for widescren entertainment options.
If Google TV is going to have a shot at displacing one of those boxes (or even joining them and their mess of cabling) it's going to have to do something radically better. And I'm not quite sure a search box interface is it. I don't have problems finding things I already know I want to watch. I do have a problem discovering things I should be watching that I didn't know about before. And in my mind that's a social problem, not a search problem.
Thought experiment: what if tomorrow Facebook announced Facebook TV? Would their default UI -- a stream of recommended items from your friends -- be more or less compelling than Google's search box?