Install it from scratch, don't upgrade. I used a couple tricks to get it to install on top of a 10.5 install, went fine. The system and filesystem dates from 10.4 days tho. A scratch install (hard disk failure) made a huge difference in general snappiness. Doubt it will do anything for folding speed, but who knows
Dump the 10.7 installer onto a usb stick with disk utility, install from there. Works like a peach.