I have had a few friends in poly relationships.
One was a don't ask don't tell type thing. That one didn't last.
One was open but with well defined ground rules that both primary members sat down and wrote together, they are still together, and have their others on the side.
One is a permanent group. Once again they have set rules, and seem to be doing fine.
I think in some instances it can work, but communication is vital.
For me I don't think it would work. I don't play well with others, and don't like to share.