Recently, a friend of mine asked me which versioning system to use so that his migration from MS Visual SourceSafe would be the least painful. Subversion, ofcourse, would be the best bet right now, but I haven't tried out GNU arch yet.
This provided the necessary impetus. As a result, I'm currently reading up on GNU arch, the free distributed versioning control system. I've used CVS a lot in the past, have given a brief try to subversion and will now try arch.
Keep watching this space for my comparison of the three versioning systems! :-)