We are using it at a couple of small sites (less than five users). It works well but does not offer the functionality of Intralink.
We only use it for preventing accidental overwriting of other users files and to retain a version history.
It does not know of the relationships between files (drawings, assemblies and parts) at all.
There is a trick to using it with ProE. You have to renumber all the ProE files back to a ".1" extension or remove the numeric extension altogether before uploading or downloading. We do this with a batch file that then calls SVN. Just right click on the file or folder and select ProE_Upload or ProE_Download and all the steps are taken for the user.
We also have a batch file that runs every night and creates a "Where Used" list. Before any user renames a file they have to consult this list and have all the parent assemblies and drawings in session, rename, then save everything.
The only pros with SVN is that it does not require as much admin or user time, works well over a WAN and requires less resources (it is not always running in the background). But I do not recommend it with design groups larger than five or so.
