Just beat it, really unimpressed. Love this game for its multiplayer. Yet, really can't believe how terrible the campaign overall has been. 1 wasn't that great, and it blew 2 away imo.
edit: the story i thought was good not great. But the development and certain plot points were done soo porly. Not to mention Marcus, still unlikeable after 3 games tsk tsk. Gameplay though was really repetitive at some points, and with teh turrets it was just awful.
Overall out of 10 this campaign is a 6.5 for me. maybe 7 on a good day.