So far, I've been a happy "Subversion":http://subversion.tigris.org/ user. I migrated "my firm's":http://digett.com VSS(Visual Source Safe) repositories, and everything's been (mostly) smooth.

"Darcs":http://abridgegame.org/darcs/ worked out pretty well for what little I used it. The interesting thing though, is that each client is its own repository. This allows you to work offline with a revisioned history of your changes. I wonder if I could set up "Tailor":http://www.darcs.net/DarcsWiki/Tailor to mirror my darcs changes to the central svn server?