Built a machine last summer, installed Ubuntu 12.04, and Folding@home client v 7.1.52. The machine is dedicated solely to Folding@home.
I run the machine headless, and ssh into it from any of our three Macs to check temperatures, do software updates and the occasional system reboot/restart as and when requested after a software update.
I use Folding@home Control on my Intel iMac to monitor the F@h client, so I can pause or stop the client if necessary.
I will say that I was really impressed with Ubuntu when I first saw it up and running. It's faster than anything else I've owned. Power consumption, headless and with the optical drive disconnected, is 110 Watts.