It's better than MW2 that's for sure, but it's ultimately an unremarkable campaign. It's opening few levels make you think it's onto something special but then those same 3 or 4 levels are just repeated throughout the rest of campaign. CoD4's All Ghillied Up level is basically recreated 4 or 5 times and the rest is just shrapnel in the face.
It's been embarrassingly dumbed down too, even for a Call of Duty game. The first half of A Veteran
playthrough is spent with the words "You are hurt. Get to cover!" on the screen because the game thinks I'm too stupid to realise that for myself when my health is low. Everytime there's a cinematic event as well the game actually describes to you what you have to do, which loses any real sort of reactive excitement. Veteran is also too easy. Like WAY too easy. The difficulty spiked 3 or 4 times but other than that it's a breeze.
But it's still a fun, capable campaign. The fact is the CoD4 has been done now, and remade by both its own sequels and competitors countless times. You're not going to be amazed by anything, and Crysis 2 and Resistance 3 both have better campaigns, but I had fun while playing it.