Has anybody check this out?
http://ccrma.stanford.edu/planetccrma/software/
It's a set of RPMs for turning a Red Hat or Fedora Core Linux install into a good audio workstation, software-wise. I know at least a couple 'fighters have tried using Linux as their OS for their DAWs but I don't think they had much success with it. I haven't tried this yet myself, but I was talking to somebody I met in Belgium who uses it as his DAW OS who says it's definitely usable.