Is it true that the ATI client runs better in Vista?

Yes this is true.

Its true for nVidia cards as well.

When you use the GPU2 client for [email protected], your CPU usage will drop dramtically.
For me, on XP my CPU usuage hits around 50% on average.
When I use [email protected] on Vista, I can't even get up to 15% CPU usage. It more stays around 3-4%

Using newer driver releases for XP has dropped CPU usage on NVIDIA cards to very low percentages. I have a 4870 that folds on a VISTA machine, but I have not tried an ATI card on XP.

I tried that, and even tried running it in Compatibility mode to no avail.

im folding on win 7. just uninstall the 7 beta and download the vista drivers and install it. its worknig for me.

I get around 68% cpu usage whilst folding on the 4870 in my sig rig.

Vista

You need to use newer drivers.

For nVidia, I can run 8 GPUs on a single core of a AMD 3600X2 and it totals 1-2% of the CPU.