The PS3Grid project has picked up a lot of speed since it branched out to include Nvidia GPU's. There are teams posting +200k a day, and this is still in beta!?
Because of this, we have dropped from 11th down to 14th, with more sliding to follow.
The clients are pretty stable. Most of the errors are user induced. Users are pushing the envelope a bit to help work out the kinks in the clients. I have have a stable Linux quad running for about 3 months. And Vista seems to be working ok also (XP has some kind of memory issue with boinc 6.3.10 and below).
http://www.ps3grid.net/
Stop by the site and look around. Don't get overwhelmed by the user/testers (most everyone). And most people forget to post what hardware they are running. But, there is some good information to be found (or ask me, I'll help).