Well, I just installed them, and jumped into Counter Stike, and I was suprised to see 33 fps, and down to the teens. WTF I thought, so I exited, turned off my TV out (tv is hooked up) and my second monitor (running off my 2nd SIS cheap pci video card) and went back in to Counter Strike, and 99fps... that is with 4XFSAA and 16X AF. on my 9700PRO.
So my advice to anyone having problems, disable your secondary monitor when play your games.. see if that will help.
In my case, it could be the half-life engine defaulting to software mode due to the 2 different videocards.. not sure,k but disabling the 2 monitors (TV and Second monitor) cleared up any problems I had.
Daniel