My wifes interest I've spoken to, he just feels like it is betrayal. He can't wrap his head around the fact that it can work. He is very idealized and is terrible with woman actually, he has this picture perfect view of how relationships should work, it's kinda creepy. I mean my wife and I are really solid and have been for years, there have been some little things lately, but nothing big. So our friends tend to have us on this awkward pedestal of the perfect marriage.
I did tell my interest that my wife and I are poly, though I chose to describe it to her as an open marriage and went into a bit more details with clarifying what we think about things and are interested in. Unfortunately it is hard for us to get together much due to conflicting work schedules and kids (she's married but separated from her husband, but he doesn't have the kids often, and regularly bails on the last minute screwing with her plans, and even though she's older than we are she has a young daughter). She showed the general playing with fire opinion where she is concerned that it's gonna burn us, so I wanted to give her some time to adapt to the concept before being specific that I was interested.
I am happy I found the forums here, it's nice to be able to talk openly without worrying about what I am saying to who.