After years of observation and consideration of such things, I've come to decide that the usual labels of "straight", "gay" or "bisexual" are inadequate to describe sexuality. Consider, for instance, the "straight" male who finds himself attracted to an attractive transgender person who happens to have a penis. Does this mean he is in fact "bi". No. He is attracted to femininity, just as he always has been. The bodily plumbing matters are basically details to be worked out.
I believe people are usually attracted more to masculinity or femininity, though sometimes to both equally. Of course, to have a physical relationship with someone is another matter, and there are many possibilities there. I am pretty entirely attracted to femininity and detracted from masculinity, though the actual details of bodily gender differences are not that big a deal for me. I love breasts and vaginas, but I can appreciate the penis as well.