I’ve been using cvs at every single job for the last 5 years. It works and it’s really stable but it’s got some annoying “features”: most notably, it does not version file and directory names so if you just want to change the name of a directory or file, you need to delete the old one (and its contents) and add one with the new name (and its contents). In the process, you lose your revision history.
Enter subversion. I just tried it out today and I like it. Frankly I love the simple zen of cvs on the command line and subversion does nothing to change that - it is trivial to use on the command line and has a laundry list of features above and beyond what cvs provides (including directory versioning). Here’s hoping every future job will use svn instead.