An awesome game if you are mature enough to over look some missing features.
That out of the way, MW2 is one of the must have games this year.
The single player mode is particularly awesome. I wont say much about it, because this time I dont want to give out any spoilers, but lets just say this game is WAY more ballsy when MW1.
The multiplayer is the main point of controversy for the MP elitists. Because it doesnt have something as simple as dedicated servers or modding, they feel they have to raise a s**t storm about it all over the net. Just proving how immature any gaming community can get when they get their toys taken away.
I can say in full confidence that IWNet is far from perfect, but if your internet connection is good (above 5 megs down) you will be fine.
The multiplayer brings smaller battles to the table, so you will have less lag and less nade and bullet spam. Battles are fought in a more tactical manner then run around and kill people. This brings more realism to the MP then cod4 had.
You now have kill streak bonuses that you can customize (like you can either set a 3 kill streak to the Predator Missile or Guard Turret).
Kill streaks don't usually get up into the upper 10's unless your in the AC130 or the enemy team sucks, so the tactical nuke bonus is not going to be used too often (its an instant win bonus for getting a 25-kill streak).
Overall MW2 brings lots to the table for those mature enough to handle the changes to the mechanics of the game.
I give it a 9.5 out of 10 because of said missing features. If they were in, I would give it a perfect score.