I used CVS for some years now and recently switched to Subversion.
I was surprised that the commands for ci, co, etc. are identical to the cvs commands -- no re-learning:
$ cvs ci
$ svn ci
But, there are additional commands like svn mv
The only difference I noted (but I use SVN/CVS only as an "intelligent backup", no more advanced things) is the way you create a new repository, but there's an excellent quickstart guide (link lost).
I couldn't imagine developing without using some kind of version control system -- it's much easier to use than cp/scp/tar/rsync :)