Left 4 Dead

Let's put it this way. It's something like a zombie mod on the Source engine. I really enjoyed the game. Great graphics, physics, and excellent gameplay. There's a strong emphasis on teamwork, which is sure to be appealing. I also like that there aren't tons of weapons, just a few types, but when you play, it doesn't feel like there are too few, although maybe adding a couple more guns would be good.
Am I the only one who has played this?