Yep, that was me. I got one "EEEEW, so you all have sex?" and a small handful of, "Oh, so you all (ahem ahem)...?" (as in "get together")
The last time I mentioned it to friends, I used the "open" term and then explained it was more like two committed relationships than casual ones. That seemed to work, and the friends who met and liked him, seemed to talk just as highly of him afterward (after being faux-annoyed with me for not telling them about the relationship structure itself for a while). I think I'll be going with this approach in the future. "Poly" seems to be a loaded word.