Thank you both NovemberRain and km34 for asking. I guess I should have spent a few words on how I define myself. I can only speak for my own definition of open, or open relationships (the plural part is important to me).
The differences to me between open vs. poly or swingers (or, even, "open relationship" singular) are:
a) open relationships seem to place less emphasis on family, live-in arrangements, and marriage than either poly or swingers;
b) open relationships seem to lay further along the sex-positivity scale than poly; no taboo around NSA and DADT;
c) open relationships seem to still allow for multiple emotional bonds (hence open relationships, instead of open relationship no "s") to coexist, as opposed to swinging.
So, to me open relationships are the best of both worlds. And, I do feel a little bit like a fish out of water around people walking around with wedding bands. Not really a turn on in bed!