There has been some growing unsatisfaction on the interweb and I have to say that I am feeling the same way.
The Sp story is ridiculous from what I can make of it. Half the time I have no idea why I am doing what I am doing or who exactly it is I am shooting at or why. It just seems like one massive set piece after another just for the sake of it.
COD4 at least gave you some sense of purpose and a rough idea of what you were tyring to do.
Also the MP is way too busy. COD4 MP's best asset was its intricate simplicity (

)
The problem with MW2 is that the maps are bloody huge, there are too many doorways, alleyways, windows, balconies, bushes, tunnels, etc for other players to spring from. Sometimes its impossible to stay alive when your being shot at from every angle.
You also seem to loose track of where your team is half the time and end up on your own lonewolving it, for all the talk of disabling party chat for a better team experience, its a lot worse than in COD4 I havent yet experienced any teamwork at all.
There are too many kill streak perks now too, its over the top sillyness. I dont like all the badges and id tags - its the same system as Street Fighter IV, it was ok there, but leave it out of this please. I also dont like the weapons you start with, most are underpowered or just unlikeable.
I also find the menus for the challenges etc, not as clear or well laid out as they were before. All in all it feels like they have turned it into an
Arcade noob-fest paradise
I will still play it and still find it ok but it certainly isnt grabbing me the way that COD4 did, and instead is turning out to be a bit of an overhyped (and for some) overpriced, let down.
Im glad I only paid £26 for it as thats all I think its worth.