I explained in my post about preferred pronouns that I no longer identify as female, and prefer gender-neutral pronouns, or ones normally used for men when no neutral options exist. As I've been discussing in mostly friendslocked posts, this change is because I've come to realize that my gender identity - my beliefs, actions, style, and mannerisms - is neutral, but my sex identity - what primary sex characteristics I'd prefer to have - is male.
As to orientation, the vast majority of my romantic and sexual partners (and I've had a fair number) have been men. I've had a number of sexual encounters and some short-term relationships with women, but have never felt very drawn to women emotionally. As time went on, I realized that my sexual attraction to women had dwindled to the point where I might be more honest identifying as "heteroflexible" than bisexual. But the words "hetero" and "straight" just seemed flat-out wrong for me.
It was when I realized that it was my gender, not just my orientation, that was queer, that I could make more sense of my feelings. Essentially, for sexual purposes, I'm a gay man. I don't have a body that most people would consider male (although that might change in the future), and that would be a problem if I were trying to find dates exclusively amongst gay men. Fortunately I have boyziggy, as well as friends with benefits.
But the more important reason I feel the need to reject the "bisexual" identity is that this label presumes there are only two sexes, or that one is only attracted to men and women. As a genderqueer I'm trying to get away from binary thinking wherever possible. I could label myself "pansexual" because I'd like to think that I'm capable of forming a sexual or romantic partnership with anyone, depending on chemistry. "Polysexual" is a word that might fit better in that regard, as it means attracted to more than one sex, but not necessarily all. But I think that term is too little-used to be understood.
Realistically, I think gay male is a more accurate representation of my sexual orientation. I've talked with some gay male friends about this and they were understanding, but I don't think the larger society would accept me with that label given my current appearance, hence I haven't posted or talked about this identification publicly much yet. (There are also some relevant specific sexual/body issues which I've been exploring, but won't go into in this public post.)
For one person's thoughtful explanations of the differences between gender identity, sex identity, and sexual orientation, I recommend reading Gender in 12 Dimensions. For another person's more in-your-face critique of binary gender and sex, I recommend reading Not Your Mom's Trans 101.