I'm glad this worked out for you but can't help but think that if a guy had a standing dynamic with a woman and then slipped his friend in instead without her permission, it would be called rape, and not a "switcheroo." The assumption by both of them that you would just be OK with it is pretty troubling as well. Perhaps I'm more sensitive about these things since I've had a lifetime of having my body autonomy overridden without my permission, but I wouldn't have been cool with that at all, even if the person was a good lover, and I was attracted to them. The end run around my ability to have a say in the matter would have killed the mood for me.