I had one instance of it, interesting at best, but wasn't something I remember being as exciting as having sex with one of my ex's. This girl and I weren't dating she was going to have a boyfriend, but her bf knew she is more sexually active with others and it was all cool and consensual there was nothing with strings attached, because we were friends for many years. It just happened and afterwards we still chilled and talked as friends. Not going to lie it was strange, but I liked it.