MW3's way faster than MW2, but I hardly ever get the feeling I should have won an exchange. I can usually say why I lost. Where as in MW2 I was saying Bull Shit! Half the time I died.
The Campaign was OK, but left something to be desired. I liked the MW2 campaign.
I haven't tried ZOMBIES yet but it looks like a combo of Operation: Threshold and DMZ which could be a good thing!