Single is good, Multi is even better.
Bucketoffish wrote this review on .
Warning though, the last mission is quit a pain. I got it maybe on my 12th try. Get through the singleplayer and hop onto multiplayer where there are a variety of game types to keep you satisfied. The most innovatative type is one that requires one team to assault buildings, and the other to defend them. That may not seem fair right? Well it is balanced, because you can pick up a repair gun that looks like a giant flamethrower that repairs parts of buildings. You actually have to aim at the damaged sides of buildings to fill in those holes.
The backpacks add a true balance to the game. Some guns are bad on their own, but great when used in tangent with other weapons. Even the base sledgehammer could be your greatest tool when using a Sneak backback, or even a Speed one. I'd say rent first, and if the multiplayer suits you than stay with it till Call of Duty comes out.