yeah. this is what I'm doing. I'm fortunate in that I have enough experience to command a pretty good rate, and I can demand corp-to-corp payment. With this, I turn around and hire inexperienced, cheap, but pretty good SysAdmins to handle customers while I'm with my client.
But yeah, 3 days a week is immensely better than working 5 days a week for someone else, then trying to get something done on the weekends.