Well, I've been playing for about 3 hours now, and have some impressions with the game.
1. Takes about an hour and a half to install, more if you don't have steam already. Pretty painless.
2. What the hell? After you start the game, it takes you to a 'main menu' with three options: Special Ops, Campaign, and Multiplayer. Clicking on 'campaign' takes you straight into the game. If you want to customise settings, first you have to wait for the intro to finish playing, then pause and adjust when the first mission starts proper - very, very annoying, especially since you have to re-load the mission if you change the video setting. Default when you first start is 640x480 - another annoyance.
3. the action is pretty immediate, once you get past the annoyances, same style training missions, setup, etc.
4. (SPOILERS) they drop some pretty huge bombshell within the first few missions - believe me when I say that gunning down civillians in that level isn't the worst thing that happens.
5. Gameplay wise, it's pretty much the same controls as COD 4, a few tweaks, the default Melee button is now E and the default special grenade is now Q - much easier to use without looking or remapping.
6. It looks good, REALLY good, better even than the first. But with that comes the flogging of the graphics and processor
7. Special Ops is good for a quick, no-story game, but beware some spoilers - it uses maps that augment the main game, so you should probably finish that first
8. The choice of weapons is BATSHIT, whatever you want - I even got a hold of a Kriss [http://www.youtube.com/watch?v=f2kEg8rEPl8] at one point.
That's all, I'll post a full-review in the next few days hopefully.