I got to play the demo twice before I left for school today.
I'm a little upset that the demo itself is barely 10 minutes of play, but other than that I'm extremely impressed (if, say, not shocked -- I've seen so many videos of this level, I actually felt like I had played it before).
The controls are a non-issue for me, but that's primarily because I'm one of those few who played Killzone 1, and the "heavy feel" is actually, well, much heavier in KZ1. Here, it's much simplified -- and I agree with those who recommend NOT fucking with the controls. I did, just to see what the dynamic was, but because of the movement acceleration, it just doesn't work as well if you mess with it.
Needless to say, I'm still getting "used" to them, but the difference in my preformance between the first and second playthrough was very significant. It just takes some play time to "get it." So long as you're not consciously trying to play it like CoD4 or something, you'll adapt quite quickly.
Visually, I needn't really say anything. The game is outstanding, and runs extremely well. I couldn't be more impressed.