You can literally fly with an 8800GTX. I'm generating about 4300PPD right now per 8800GTX. My 9600GT comes in around 3500ppd. The 8800GTS G92 cards I believe get over 5K PPD. If you have a GTX 280 I believe they pull over 8K PPD.
Check out the stats page. Just over 9000 GPUs are churning out 1PetaFlop. With a little help the GPUs will overtake the 48K PS3s.
In order to use the GPU folding you need to have a CUDA enabled driver, aka 177.35 or above. I've used the 177.35, 177.39, 177.66 drivers and all of them seem to be working. The latest GPU client can always be found in this thread. http://foldingforum.org/viewforum.ph...4d8bf1a5506029
Here is the latest client as of 7/17/2008.
If you need help installing it just ask. A couple of notes, if you are using SLI it will unfortunately need to be disabled for this to work, so if that's a problem you can probably just use the SMP CPU client instead. There is also support for Radeon cards as well.
For Single GPU users I recommend the Systray installer, as it is the easiest to use and provides a GUI to setup and manage the client.
One more point of consideration. The group # is 35216 and is the NVnews OSNN and SP group. There is an older group floating around so some people were folding for the wrong team.