From someone who has subbed out jobs for the past 4 years or so, I would say make the investment in a machine, if you have the right volume. It may depend on the area you're in, but it's rare to find anyone who cares as much about your jobs as you do. True, the liability of screwing up prints is now on you, but the return on investment (at least in our case) has definitely paid off.
We purchased a Roland XC-540 in Sept. '09 and have had it running almost nonstop since. It's a great machine, and Roland's Versaworks is a really great beginner RIP. Not shelling out $3,000 for RIP software has to figure in there somewhere. We now have an HP L25500 running alongside the Roland and I'd recommend both machines to anyone.
Hope this helps.