Okay, so I just finished the demo. This is my first time playing the game as I was not in the beta, so here are my impressions as someone who does not really care much for FPS games:
First off, the game is absolutely gorgeous. I've never seen a game so clean... I found myself staring at the set pieces at times instead of following my teammates. There's no aliasing, it's unbelievable! Even the shadows are clean. Oh, and I didn't see any framerate issues.
Secondly, the controls. After reading some of the complaints here I was a bit worried, but really... I had no issue whatsoever. I found them comfortable and absolutely natural, no real learning curve or anything. I used the default setting, by the way. Very smooth, very nice. Didn't find myself having trouble even with a lot of enemies coming at me at once. I find shooting from R1 to be really easy for me and couldn't imagine trying to use R2.
Even though the demo was a bit short... it did give me a good idea on what the full game would be like. The AI is pretty sharp, but I managed to get through without dying, though I came close once inside the warehouse... All in all, as someone who rarely plays FPS, I will be picking up Killzone 2 come February 27th. I feel that if I don't, I'll be missing out on one of the best games this generation. It's not often the hype turns out to be real.