It looks boring and repetative. Once you have gone through your 100th portal, and viewed the dull black walls and bright green neon glow textures for the millionth time, all will be left is another FPS, all novelty will be dead, because they havent taken a series of novelties and applied one to each section, they have taken a series of novelties and stretched it over the span of the entire game. Once you have played an hour of it, you've played it all.
I watched the whole movie through and they showed us several differant sections of the game. It all looked the same to me, I was bored to death.