I think there's some value in identifying our social, romantic, and sexual orientations separately. One can be primarily homosocial and heterosexual, for instance, as the majority of self-identified straight people seem to be.
Of course, that stance gives away the fact that I don't think orientations are meaningless or 'bogus.' I don't think the argument that "you're not really homo (or hetero) sexual because you're not attracted to every man (or woman)" holds water, and the claim that we identify our orientation by the sex of the people we've found attractive is rather simplistic.
I don't identify as gay just because everyone I've found attractive or responded sexually to has been male. I identify as gay because the thought of whether or not I find a person sexually attractive only occurs to me if that person is male. I just don't think about women that way, though I have tried. Sure, there are tons of men with whom the very thought of sexual activity makes me ill, but the fact that I have to phrase it that way just shows that I've thought about it. I think about it automatically when I meet new people, or even if I just see their picture on the Internet or pass them on the street. Straight guys tend to do the same with women. In fact, many women believe that's how their gaydar operates - just noticing how a man looks at them when they first meet.
Bi/pansexual people- seem to tend to believe that everyone is bi. I'm not sure why, and I'm not sure how to explain that we're not. And that doesn't necessarily mean we're not open to dating trans people, it just means that we'd not see such a relationship in the context of bisexuality/gender flexibility, but rather as simply being with someone of our preferred gender with a complicated medical history. Not everyone has to be bi for trans people to be accepted.