I've definitely been bi curious, but it seems like it's going to be always in the "fantasy" category for me as my LTR is not interested in any kind of three way type stuff. I've done a little jacking off with other guys in the past, but nothing more than that. I'm alos pretty particular about the type that I'm attracted too and it seems like I've probably reached an age where that type would not be interested in me.
For me though the fantasy has almost always involved a female being present though. I really seem to need that feminine energy present during sex for it to feel right.