With so much denigration by those who've posted comments, I felt it was time for someone who likes the movie to post something.
I saw it in the theatre in 1971 and came away feeling like I'd seen something special. Now, I was already quite a fan of Peter Kastner for his wonderful performance in 1966's 'You're a Big Boy Now', so it's quite possible my liking of him coloured my critical thinking.
But I don't think so. I liked it a lot - in fact, I like the counter-culty free-sex vibe of so many movies from those magic years 1970 and 1971. And apparently there's a reviewer with the New York Times (Howard Thompson) who found it to be as delightful as I did.
Peter Kastner was a very likable young man. He was capable of expressing many emotions in a really charming way. He should have become a better-known actor.