I second that. On my 17" iMac with ATI X1600, Half Life 2 runs on 1440x900 with all settings maxed except anti-aliazing, and framerate is way beyond just playable. Nice coding, Valve!
I've somehow managed to fix the problems by reinstalling everything barring XP itself and HL2. No crashes at all! It is so very well coded. Runs on my 2ghz P4 in very high settings too.