I can speak to this, having shared a lot of MDMA experiences with a self-professed sociopath who was formerly a good friend until he crossed the line a bit (harmlessly).
The experiences seemed to be more hedonistic for him than anything... However -- and this is big, imo -- the MDMA did help him open up about a lot of things (for example, being a sociopath) and other kinds of darker predilections that he had kept inside / experienced in the past. And I think it made him a much better person for it, in all kinds of ways, just getting this stuff out and sharing.
But in the end, the relationship fell apart because I couldn't deal with the subtle manipulation that he would constantly try to get away with (hilariously assuming that I couldn't pick up on what he was doing, which was often very obvious -- a sociopathic trait, being unable to relate and thinking oneself superior). We had a lot of good times, and I think about those days often. In the end I just couldn't handle the quirks... which might say more about me than him.