I'm just a newbie here, but personally I really like the fact that polyamory has a less than specific definition. It makes me feel like there are less automatic assumptions that go along with it, unlike some other labels that carry a whole set of stereotypes. If I tell someone I'm poly, they generally don't even know what that means, and I don't mind that at all. I'd prefer to explain the specifics of my personal relationship structure than rely on a label, and that would be especially true if I were talking to a possible romantic interest.
I understand the points about polyamory relying on trust, honesty, etc. But I agree with those who have said that those are simply good tools for any relationship with other human beings. If someone else says that they're poly, I assume that means that they are not romantically monogamous, and that anyone they are involved with is aware of that. My assumptions stop there. I don't assume I know anything about their values/ethics/specific relationship structures/etc., just like I wouldn't know any of those things about an individual based on a label of bisexual/gay/straight/etc.