I have never done that or had it done to me but I told my wife a few years ago that if I expected her to lick another woman's pussy for my pleasure that it would only be fair for me to return the favor. I was pretty relieved when she said that did not interest her at all! lol
My gf told me last week that she thought it would be REALLY hot and that it would make her extremely wet to see another man suck my cock or to see me suck his. She and I have not had a threesome yet with either sex but she really wants to and I would like to think I would be willing to go through with it for her sake... I am more open to that now than I was before anyway