So I went ahead and removed the popcorn on the ceiling ... boy was it
tough ... there were so many layers of paint that I went thru 5 gallons
of water for a 300 sq ft ceiling in order to get the stuff wet enough,
and even then almost half the ceiling didn't want to come off without
major persuation. At the end of it, the whole ceiling needs a skim
coat, which fortunately a friend of mine has offered to do (he's a
pro). Looking back, it would have been way way way easier to just
drywall over the ceiling with quarter inch drywall.

Thanks for all the answers,
Harry