Question:
...where there is rust: under _one_ of the side windows - goes all along the
bottom of the seal, and on the inside of the sliding door - all along the
inside of the very bottom lip. That's pretty much it.  Are these real bad?

Answer:
Depends on what your definition of bad is [sorry Mr Clinton].  I would say
this is a common failing with VW products and others.  Water accumulates
behind the gasket and in time creates a problem.  Fixing is a matter of
pulling glass and gasket, sandblasting, treating with some of the better
rust prep chemicals, repainting, and finally re-installing the glass.  Had
correspondence last week on Dow Corning high vacuum grease, which I like to
use in the re-install phase, both for easy fit betw gasket and metal, and
for helping to seal the surface of the paint inside the window opening.
It's expensive, but you only need a little bit....... should be easy to beg
maybe � tube in the univee labs at Madison.