I remember seeing it in San Lorenzo, CA, opening weekend '71. The old Lorenzo Theater was packed. Went with a couple of buds, back when you could bring your own snacks (Fritos and Space Food Sticks!).
When the curtains parted and "Metro Goldwyn Mayer presents A Dan Curtis Production" appeared. The first notes of the theme song played, a raucous mix of applause and cheers rang out! Two hours later we saw Barnabas get his just desserts.