way I use these words, I absolutely don't use "straight" as the same as "heterosexual" (in the same way that "gay" doesn't mean "homosexual" either). if I kiss a boy that's a hetero kiss but sure as fuck isn't straight. "straight" is the opposite to "queer" (to the level of the metaphor, even), and a hetero relationship sure can be queer.
when I kissed girls before transition that was straight-passing and I would attempt to have straight relationships to various degrees, but even before finding my gender I always ended up queering it anyway, cos I'm not straight and can't ever be happy in a straight relationship, independently of the genders involved.
it's even the case that a homosexual relationship could theoretically be straight in my sense of the word, if the assimilationist agenda ever succeeded. in the current society it's impossible, but gay marriage was a move towards straightening homosexuality, and before this wave of transphobia set them back 30 years, the assimilationists were well on the way to have fully straight same-sex couples.
myself I'm on Sylvia Rivera's camp, I'm fiercely hostile to any hint of straightness in my life. all the stuff I've done with men has been as queer as it gets, whether I was already living as a woman or not.