It's the Source engine and it looks pretty much in line with Source engine games.
If anything, I think they need to work on the animations. I'm a little more annoyed at the hiccups when, for example, zombies are right next to a player and attack.
*edit* What Rocketpig said above is exactly true.
Speaking of PC's... I'm going to need to pick up a new video card soon. 8800gt's are around $150 or so, hopefully I can get some money and they'll go down even lower in price within a month or two.







