At first i was pleasantly surprised with the graphics (especially the shadows casted by mercs' flashlights) but then i decided to boot Chaos Theory on my x360.
I was surprised to see it runs perfectly, i'd even venture into saying it's smoother in places. And boy, that game was gorgeous; i used to think Double Agent was quite a looker (actually, parts of it are, others are quite underwhelming) but after seeing chaos theory in 720p (upscaled or not) i demand much more from an x360. But after all, we've always known SC5 was the real deal.
Having said that, i had a very good time with the demo and i'll probably buy the full game when it's available in europe.