Hi all
I had a great FPS increase using this competitive config from the fellows at thebrink.tv - maybe you will too. Here is a link: http://thebrink.tv/forums/viewtopic.php?f=8&t=170
Obviously you will be giving up some graphical niceties but its worth it for smooth gameplay. ATI user here, muddling fps since release, this solved my problem. The config is notated with every change being made, I suggest going through it and just customizing to your liking. You will especially want to set the FOV and resolution settings to your preference, or you will load into something very alien on your first try.
FYI the default FOV is 70, but I prefer 90.