I got Left 4 Dead as a gift from a friend, and despite not being into the whole zombie or horror genre, I truly enjoyed it. Only having 4 campaigns was little disappointing I agree, but overall I had a lot of fun with it, and still do. Something I found odd was my team-mate's AI, when I played the multi-player, and had a friend join me, the rest of the team when computer controlled seemed, smarter. When I play single player, they seemed dumb as rocks most times, getting stuck in places and so on.
I don't get to play PC games as much as I'd like to these days, but Left 4 dead, is one game I would love to see an expansion pack for, more campaigns please!
Love the game, and the review.