They say the difference between gender and sex is that gender is a social construction, and sex is a physiological one. It seems to me some people defy gender/sex norms because of reasons related to gender while others for reasons related to sex, and I think there is a distinction between the two which is significant.
It seems there are some who take on the appearance of a woman as an expression of their femininity (this is an MTF zone, so I'll stick with assuming that is my audience, it's simpler.) For them, I guess it's not so much they feel as though they are a woman per se, but that they are feminine beings who need to express their gender this way. You also have the people (maybe they are the same people) who talk about rainbows and spectrums and being gender outlaws and who hate the concept of sex being binary. These are people dealing with issues of gender identity, and I never actually realized they existed till I read these boards for a while.
Peeps in the other group are experiencing conflict with their sex, not so much their gender. This is the group I find myself in, as I truly have no conflict whatsoever with my gender identity. I have problems with the gender role I'm expected to play in society, and I have problems with my body being wrong, my identity however is fine. I don't dress in women's clothes to express my femininity, I dress in women's clothes because that's what women do, etc.
All this business of spectrums and rainbows is cool and all I guess, and maybe such a thing does exists as it relates to sex, but the condition I am dealing with absolutely conforms to the gender binary norm. I have no desire to be placed into a 3rd or 4th or 8th sex category. I mean it's fine if that's how somebody else feels they should be categorized, but I don't want to be included in the crusade.
I was born a girl (your brain is who you are after all) with the wrong body, so I consider this a purely physiological disorder. As such, it should not be called "gender identity disorder." If you must call it something, it should be called "sex identity disorder" ..I guess. I would actually consider this to be a form of intersex (of the brain) more than anything else.
There clearly is nothing wrong with any of the expressions or conditions in the spectrum of gender/sex identity. We do all face similar issues, both sides may even benefit from SRS for all I know. Anyway, our similar trials do make it possible for us all to be able to offer each other support. I think the idea of breaking away from the "umbrella" is pure silliness. Together we are still a small group and wield very little clout, which is why we should take whatever help the gay community may offer as well.
It doesn't hurt to understand there are some fundamental differences between people, even if they convene under the same "tent" as you say, though it is naive to think society will ever see you as a woman, no strings attached, in your lifetime. Even though that is exactly what you are.