MW2 for the PC is an unfortunate let-down, only die hard fans of the series will get their moneys worth.
MW2's campaign begins a few years after the end of the previous game and has the usual COD formula of frantic scripted firefights and stunning set pieces. As with the other games in the series you find yourself in the shoes of various soldiers in several locations around the world, mowing down masses of enemy troops with authentic military hardware.
The gameplay itself is unchanged in all aspects except that enemy troops will no longer respwan indefinitely which many people considered a pain in the previous titles. The framerate is smooth throughout and the visuals can be tweaked to run on even a lower end PC. I managed to run the game on max settings and the game is beautiful to behold for the most part, though the 2D backgrounds in some places look noticeably awful. The difficulty of the game goes from easy to very difficult depending on which setting you choose, though this game is more difficult on veteran than previous games, mainly due to IW's illogical decision to remove the ability to lean, yes, I know, console gamers have had to put up with this for years, but on the other side of the coin, they have an auto aim feature, which no respectable PC gamer would even think of using.
The in game sound is solid, and the battlefields sound realistic with music kicking in as the action heats up.
The story itself, in my opinion seems to have been stuck in without much consideration, and there are times when you'll be scratching your head and wondering what is going on.
The multiplayer is a huge letdown on the PC, and while there are indeed a lot of new weapons, maps and unlockables - there is no mod support, no dedicated servers and a limit of 9 v 9. For the most part this new system works reasonably well, but some of the larger maps simply beg for more players. The downtime between games is also a pain, you're forced to wait 60 seconds between games, followed by another 40 or 50 seconds after the map loads, then even more waiting if the host leaves and the game selects a new one.
The all new co-op mode called Spec Ops can be a lot of fun if you have a friend to play it with but it becomes old quickly, and often you will find yourself amused at the games logic as it sometimes gives you ridiculous weapons to complete the mission at hand, though this isn't a huge issue since you can often change your stock weapons at the beginning. The big con of this spec ops mode, in my opinion, is that it only supports 2 players, it could have been so much more had more time been spent on its development.
It is a shame that IW have taken this direction with the PC version as it could have been so much more, as it stands at the moment there is really no advantage in owning the PC version over the console version other than greater precision with a keyboard/mouse setup.
If you were a fan of Modern Warfare 1 then I recommend this game for the campaign but stick with MW1 for the multiplayer. If you can rent a console version of this game then all the better to save yourself some cash.