As a bi guy, I'm able to appreciate both masculine and feminine features. Pre-op transwomen bring the best of both worlds. It is a nice surprise to see a penis down there, but of course it doesn't take away from the fact that she is a female otherwise. I wonder if you have to be some degree of bisexual to appreciate a transsexual since they have both masculine and feminine traits?
It is important though, that transsexuals be looked at exclusively in a sexual fetish kind of way. They are women, just like any other women, who happened to be born as the wrong sex.