Downloaded this a few days ago, and it rocks. Alien Swarm feels like a hybrid between Natural Selection and an online Co-operative version of X-Com. Anyone else here playing it?
And when I'm sad, you're a clown
And if I get scared, you're always a clown
I got it in CD-Rom when I bought some random issue of PC Gamer. As I have no internet connection at home, I've been messing around its single player a bit.
Pretty fun. It'd be interesting to see how it plays out in multiplayer.