I'm three levels in to the single player (I have no interest in multiplayer, as much as you guys love it, because I'm far too in love with MW2!) and so far I'm quite enjoying it. I never played the original, but I'm finding the characters extremely likable and the gimmick of blowing everything the fuck up is doing it for me. I love pelting a grenade launcher into a hut full of enemies and seeing it fall around them, or running away from a tank and having all of my save places crumble to the ground.
It seems a little bit... generic? I guess that's the best term for it. There's nothing wrong with that - everything has been fun so far - but nothing has really stood out to me as a great moment. I wasn't expecting it to be anything more than a fun shooter, though, so I'm overlooking that.
I have to say it looks stunning on my PC too. I have everything cranked up as far as possible in 1080p and ... well, I'm glad I resisted buying it for my 360 or PS3 now.