I preordered this game from Mighty Ape and received it today. The moment you load the disc and the game start, you know you're in for something good. The opening movie is just awesome. You can see every details on Visari's face. The game graphic also looks gorgeous and there are heaps and heaps of enemies to shoot at one time without any hiccups (and that's only my first two stages).
Another improved feature for this game and makes it better than the previous title is the A.I. Man, those Helghans are smart. If you take cover they'll try to kill you with grenades or kill you with melee attacks if you go near them and aren't quick enough to knock them first.
Killzone 2 is a great game. I like it even though I'm not a fan of FPS. I'll give it 9.5/10 (nothing is perfect) :P