I thought I would jump in here and answer or give my two cents also..
For me personaly (the female half) we have only been with one other couple. I was so busy I really didnt get to see anything..
But I heard it all...
And I must say that in itself was a huge major turn on for me. Just knowing he was enjoying himself so much and that the other woman was having a good time also. I can say that it didnt bother me in the least..And am looking forwrad to it happening again...
We have had a a few threesomes with an ex-gf of mine. Although it was just soft swap for them. It was also a turn on to see and hear that.
Amy