hey i didn't know if anyone said anything about this, so i'm making this topic here. there are new catalyst drivers and they're 4.12 beta and ati recommends them for half-life 2 (*if you have Radeon 9500 or higher). i installed them and i notice a significant increase in performance in CS:S but haven't tried hl2 much since i beat the game before using these drivers. all i know is CS runs about (it seems to me) 30% faster. i was able to turn up all my visual effects (except i don't use AA) and it runs even better so i highly recommend those of you with hl2 and an ati card to try it out!
here's the link to the 4.12 BETA driver on ati's website
http://www.ati.com/support/infobase/4701.html
*maybe you should make this a sticky so people know? i never saw anyone else talking about this around the forums.