I have played it on my work PC, which is a dual 2.4GHz pentium 4 with a radeon 9600 XT card ... and decided not to bother anymore. I had to play at 640x480 low details to get any kind of decent frame rate (then again I am a frame rate nazi). I would probably endure the crappy graphics at those settings for multi player, but for single player the first time through I want the full experience! I have decided to put the game aside until I can upgrade my home PC ... i.e. if I can steal my wallet back from my car
Here is a good article on the kinds of frame rates you can get with different hardware:
http://www2.hardocp.com/article.html?art=NjQ0