I don't like labels, but i would have to say that when it comes to my sexuality i would say i'm "trisexual"- i'll try anything!
Seriously though, i consider myself bisexual. I'm not a 50-50 mix (so few are), but i could never say i'm straight as i love cock too much! I prefer the overall look of a woman- from her face to her shape, smell etc, but i have always preferred cocks to pussy. I love pussy, especially unshaven, but cocks are so much more fun! So a Tgirl is for me, the best of both worlds: the beauty of a woman with the best bit of a man!
As for considering oneself "straight" whilst loving Tgirls... i can understand that to a point. Even the most well endowed of Tgirls is more "female" than the sum of her "male" part as far as attraction goes for admirers, but ask any "regular" straight guy if he'd suck a cock if it was attached to Halle Berry or Beyonce and he'd probably say no!