Snagged CoD4 from Steam and spent some time playing it. It's yet another installment of the good old Call of Duty series.. nothing much has changed except for the setting.
As usual, the game itself is more about immersing you in a cinematic experience than anything else. A lot of the one-liners are pulled from iconic movies. Bad guys will keep swarming out of spawn points periodically until you finally figure out you're supposed to move up and take the house they're coming from in order to stop the script trigger. You're squadmates' main job seems to be running directly into your line of fire and blocking doorways so you can't run back through a door to find cover from a grenade. And, if you happen to run out of ammo, just pick up one of the 7,000 guns laying around on the ground from previously conquered enemies to keep bringing the pain.
The game has added in some new mechanics, such as stealth movement in the SAS episodes and guided missiles in the form of firing a Stinger and a Javelin. And I've got to admit that the opening level is really well done (I'm on a boat!) from an immersion standpoint. Haven't tried the multiplayer stuff yet, but that's on the todo list.
Overall, not bad entertainment, but I wouldn't say it's groundbreaking in anything other than scriptwriting and the fact that it's not yet-another-WWII game. :)