I played it on a system with 1.5ghz processor, a 96mb videocard and a 15'' screen. Played it on settings that were less than recommended. I was able to finished about half the game but when I got to the part where you're on a boat outside, my computer couldn't render anything correctly and did nothing but lag.
Aside from that the game is pretty damn fun. Better than DooM 3 as far as I'm concerned. DooM 3 was fun. But Half Life 2 was better it felt.