Brutally detailed, incredibly bloody, and sadistically satisfiying.
The best part of the game occurs when you open up on a Helghast from a close proximity, and watch as your bullets tear them to bits. Every kill is different, and none of them look the same....well maybe headshots :) The weapons deliver different experiences, all handling situations in a seperate fashion.
The online shines in Killzone 2, but it will take you time to adjust to the feel and controls. Once you do, you'll enjoy earning badges which unlock weapons, classes, and different abilities. So while you may not enjoy playing online at first, keep going till you unlock some badges that'll expand what you're able to do. While most online shooters today push the team aspect, Killzone 2 really requires that your team uses different badges to accomplish the mission. When the abilities are used correctly its a beautiful thing, so get online and enjoy.