Well, I own it, and I play it a lot, but it has its disadvantages.
1.) Those freaking dogs that jump on you and make you hit the melee button at a specific time are just stupid. They shouldn't be in the game, and they are annoying.
2.) The grenade indicator blows, and of course, the AI is awesome at throwing grenades. You will die from grenades far more than you like, especially on higher difficulties.
3.) It's really really really scripted. This isn't necessarily a bad thing, but understand that you will rarely have the ability to flank the enemy due to the limits of the battlefield you are on (in single-player).
4.) It's really really really short. I beat the entire game on Hardened (2nd highest difficulty level) in 4.5 hours. My friends and I joke that they named it Call of Duty 4 because that's how many hours it takes to beat it.
5.) Online play is cool (especially on 50 man PC servers), but the level up system puts new owners at a heavy disadvantage. Luckily, there are some "Shipment" map deathmatches designed to help you level up faster, but it still kinda sucks to have to spend a bunch of time leveling to have good guns.
Some positives are: The campaign has great pacing and story. It's like playing through a very good action movie. Although the leveling up kinda sucks, the online is very good. You'll find hours of enjoyment, especially on the PC version with much larger servers than the console versions. I'd definitely recommend it to fans of PC FPS games, but don't go in expecting it to be better than Orange Box on PC... you'll be disappointed.
