We use SVN for all of the development projects related to Jamoma and SpatDIF. SVN works well, and the Versions client for Mac OSX is excellent.
Still, for me there’s one caveat: SVN requires you to be online to update and commit changes, and I don’t have internet access at my studio.
For a while I have been curious about GIT. It seems to gain a lot of momentum among Rails developers, and one advantage seems to be that you don’t depend on network access to track changes done locally.
A post to the Pd list a week ago pointed to git+svn, enabling one to use GIT locally, but synced to a central SVN repository. It would be nice to install GIT and check out git-svn over the next few months. There seems to be at least two books available: Pragmatic Version Control Using Git and the free online Git Community Book.
Recently GitX was announced, a git GUI specifically for Mac OS X.