Having played both this and MW2, I echo many of the comments made in other reviews that this is the superior game. The single player is very good and whilst the storyline isn't that original, the missions themselves are top notch! I thought the banter between the soldiers added to the realism and it kept me playing till the end.
However, multiplayer is where this game truely shines and I cannot stress how brilliant this game is online. It's very teambased and it rewards you for reviving people as a medic, dropping health kits or ammo, repairing vehicles, spotting enemies, etc. The game seems to be quite well balanced and it is a refreshing change that snipers are not as deadly in other online shooters. Yes, you still get campers, but if you're smart, use cover and try to sneak up on them, then they aren't too much trouble. Vehicle combat is brilliant, aside from the helicopters which can be a bit tricky to control, but with practice they become managable and can truely change the game in your favour. Even without a headset (like me) it is easy to work as a team, as the select button allows you to designate target objectives or ask for ammo/health. It is also nice that I've haven't had the misfortune yet of hearing obscenities or bad sportsmanship, which says a lot about this game.
Overall I'd highly recommend this game! You will not regret it.