vc-hooks

I recall that it was decided at some point that loading vc-hooks was not good citizenship, because it was breaking something. What was it? pcl-cvs? (If it is the pcl-cvs problem then it is probably no longer true, since the new rewrite from Stefan Monnier works in concert with vc.el) I am asking because ediff uses some functions from vc-hooks.el to determine the version control system of a file, or if the file is checked in or out (in case of RCS). Some version-related things in ediff don't work correctly if vc isn't loaded, and I don't like the idea of copying functions from one package to another. --michael