Interesting timing. My team at work just (as of yesterday) moved to Subversion. The main thing keeping us from doing it earlier was external collaborators who were used to cvs, but that's been taken care of.

Being newer than cvs, svn doesn't have quite the number of friendly GUI clients, editor integration, etc. but it's getting there. Since XCode can use it, and there are a couple good OS X GUIs for it, I'm happy so far.