I have had the pleasure of both MFF and MFM threesomes (both before marriage) and both where wonderful experience. Setting the rules first and foremost and being comfortable enough to talk it thru seem to be the most important in my opinion. If you can't talk it thru and openly discuss the pro's and con's then you shouldn't be in the situation to begin with.

Hubby and I have talked a number of times of adventuring out to try these again. Again the rules would be the issue.

But I have to say it was amazing!