I will say this. As someone who has played the Left 4 dead 2 demo extensively...It ROCKS!!!
It's better than the original in every way. Valve has done a remarkable job at making it stand out. I thoroughly expected to be disappointed. My only complaint about the demo itself is it is too short and too easy, problems that the full game will remedy.
It looks like a graphics mixture between HL Episode 2 and TF2 but with the L4D game engine.
Children, this is why you shouldn't play video games while on crack...