Quite honestly I haven't been all that impressed by Microsoft SourceSafe (even with SourceOffSite), or CVS. Subversion could easily be described as "CVS done right". It's very similar in many ways, but, for instance, Revision numbers are per-commit, not per-file as they are in CVS. I've been eyeing Subversion since earlier this year but finally started using it three weeks ago or so, and have only run into a few minor issues because I didn't read the manual ;-). Subversion development seems to be moving forward at a quite steady pace, and it looks very promising. Touch wood.