i watched that 20min long game play demo a little bit ago. I was and still am blown away. Not only the engine, but the sound of things like the guns, little noises. I also really like how none of the AI is scripted. It takes everything into consideration and chooses the best route to either cover you, you cover them, etc etc. I was impressed by that.
As far as the engine goes that thing sure is something else. I don't even know what to say. It's just way to cool for it's own good really. The only downside is that i'm gonna have to upgrade my computer hehe.
I can't wait to see what else this game is capable of.