We use Clearcase under both, UNIX and Windws.
I have tried CVS and RCS, the good thing about CVS is that is free (at least it was on those days). They are all right but as soon as you get Clearcase life is great.
I am not administrator and I don't set up Clearcase, VOBs, groups, etc...as a user is great and very powerful. We use it for FPGA and Software development.
One thing I liked about RCS is that you can buy an add-on which allows you to compare .DOC documents. Something Clearcase does not do.
Regards.
-Maestor