I forced my girlfriend to rewatch this classic from 1971 last night. It truly is a crappy movie that doesnt suck. Its semi-cheezey but it carries a sense of foreboding all the way through that's really stifling. And besides, Judy rocks! The special effects are silly by today's standards but they get an a for effort.
Dont confuse this with the crappy movie that DOES suck, the A&E version that came out earlier this year.

For your viewing pleasure: www.youtube.com/watch