While all the early Woody Allen films are funny and worthwhile, this is probably the most uneven to my taste.
Allen took the famous, serious non-fiction book about sex, and turned it into a series of short comedy pieces. A couple segments are pure genius (inside the male body during sex, Gene Wilder falling in love with a sheep), a couple are pretty good (Woody as a medieval court jester trying to have an affair with the queen, who is locked into a chastity belt, a mad scientist creates a giant milk squirting breast that goes on a rampage) and a few are real duds.
Also, of all the Allen films, this might have the weakest DVD print/transfer quality.
It's bizarre and disturbing that a lot of Allen's brilliant early work seems to be going out of print. Hopefully this is just a temporary state of affairs, and better re-releases are ahead. But if you're a fan you might want to grab copies of this, Bananas, Interiors, Annie Hall(!), etc now, while you can.