I have !!!! .................. in my head that is !
... and, I bet I'm not the only MumsNetter who's at least wondered what it might be like ?? Mind you, when such - ahem - thoughts cross my mind, the party in question is populated, strangely enough, by the likes of Russell Crowe, Edge, Sean Bean, Gordon Ramsay, my old rather gorgeous vet - and other such fanciable men.
In reality though, I would be far too embarassed to reveal my body in all its "glory" to a load of strangers even if they were very broad minded. And of course, the emotional fallout from something like that can only be guessed at before the event - which personally, I think, is quite a risky strategy. I would be terribly worried that either one of us might form an emotional attachment to someone else & really do believe that your relationship can't be the same as it was before. What if one of you likes it more than the other and wants to do it again but the other person doesn't ?
Best kept as a fantasy IMO.