This is an ongoing discussion with my spouse who claims m/f/f is the menage norm. Of course, I can't think of anything much hotter than an m/f/m combo. I like reading it, and I enjoy writing it. One of my favorite authors is Samantha Kane, particularly her Brothers in Arms series.
There's just something about two guys unbending enough to show love for each other that's incredibly sensual.
So what I wonder is -- am I the weird one, or are m/f/m threesomes really hot?