I have never sat and watched it from beginning to end and have only seen clips and bits of it. I always thought of it as a strange riff on Orwell's 1984, but I was reading something in passing the other day that said it was "the nearest we are ever likely to see an adaption of THE PRISONER on the big screen."
THE PRISONER was not something I would have immediately connected to this film, but I am intrigued somewhat after having read that.
Harlan Ellison loved this film too, I believe, so I might give it a go sometime soon.