I've been playing it for a couple of hours now, multiplayer is a bit laggy, and IMO the graphics ain't as good as MW2. I also don't like how the players run, it looks like your team mates are a bunch of gays scampering around, and when you run it makes that horrible out of sync scampering sounds, every stride you make there are 2 or 3 scampering sounds, it's hard to explain, and it's annoying.
It's not a bad game, but after playing MW2 for the best part of a year it's just going to take a bit of getting used to, I'm sure it will grow on me, I thought it would be an all round improvement MW2, but so far I can't say it is.