I picked it up 3 hours ago because it was $2.50 and I was pissed at PD for not having GT5 at the moment, so I figure I buy it cause I was bored. 
 
It's pretty good.  For a 2 dollar game, I already put almost 3 hours into it. 
 
It's like COD but not as sucky.  No spawn campers, the team works like a team, no kids on mic (there was one but he got kicked), and the graphics are good enough it runs fluidly on my weak 9400M on my MBP.   
 
The only problem I have is that you are locked to set classes, and for some reason people keep screaming medic but there's no medics in the game.   
 
For $2.50, not bad at all.

Welcome to the world of Valve games. If you like that game then you should definitely check out other mods that people come out with. 
 
Sorry to hear about GT5. I'm already putting away money for it in hopes that it comes out soon. Till then I'm playing Gran Turismo 4. I think I'll go down to Gamestop and look for Gran Turismo 3 also. Just to fill up my PS2 collection.

This topic's kind of old, but I just bought the game too, and yeah, it's not bad at all. I've been playing some zombie matches and it's like a cross between Nazi Zombies, and L4D. Really fun. It's taking me back to the good ole days when I actually played PC shooters, like CS.  
 
I recommend it if you guys want a fun multiplayer shooter that's less than $3.

Yeah this is a very good multiplayer game, I have been playing it for years now and I'm still having fun, unlike COD.

It was ok when it came out, but unfortunately Valve stopped supporting it and there are several bugs and balance issues that could've been addressed.

I put this game in my cart on Steam while it was on sale yesterday and forgot to actually buy it. When I remembered it had already gone back to 5 dollars. I might still buy it though.