I think the differing opinions comes from the gamers playing the game. Call of Duty fans who generally arn't too keen on working as a team and arn't the best shooter players won't enjoy it. But those which enjoy heavy teamplay and objective modes love it.

Also there's a distinct difference in those criticizing the singleplayer portion, when the game was designed pretty much for MP at heart. What pisses me off is once again another example of reviewers lowering scores for poor singleplayer yet praising the multiplayer, but then when a game comes out with poor multiplayer and great singleplayer it doesn't hurt the score whatsoever (e.g Dead Space 2).

Then just rent it.

LOL