This is one of the very few movies out there which are very erotic without being pornographic, despite there being only a very rudimentary plot. There's not much live sound or dialogue; instead, the actors do voice-overs describing their experience, why they participated, etc.
It's a document.
It's mind-blowing.
I can totally understand why nobody else ever tried to do something like this. There already is something like this. This. :-)
NB: The producer doesn't have the rights to distribute a DVD version. I've also never seen it being sold anywhere; one may email Mr. Boerner and order a copy on VHS.