It looks like the GTX 580 won't be very good for folding
...According to sources it can be as many as 300 million transistors that NVIDIA has been able to cut in this way. The effect is that GF110 will be a GPU targetting only retail and will not be as efficient for GPGPU applications as the older siblings of the Fermi Tesla family...GPU clockspeed is said to be 775MHz, with 1544MHz shaders and 1536MB GDDR5 clocked at 4008MHz...
Source
EDIT -> I found an interesting response:
"They took out all the redundant, switched off HPC caches, but are ADDING CUDA cores. HPC functionality was only active in multi-GPU Tesla + rack units anyway AFAIK."
So I am guessing that making assumptions won't be useful until the real product is released.