I think this is such a very interesting topic.
I am MtF, about 7 months on medical HRT (herbals a year before that).
I identify as Pansexual, as I've had sexual experiences with cis-women, trans-women, cross-dressers and men.
I've only been out as trans for just under 2 years. Interestingly enough, all of my sexual experiences, before coming out, were only with cis-women.
I feel like I have such an advantage over some (arguably most) people as I have sampled most of the "gender buffet" and and really have a better understanding of what and who I like. I find it short sighted for people to claim they're absolutely straight, without ever challenging their selves, by only sharing sexual experiences with their declared sexual preference.
How does one know they don't like "green eggs and ham", if they've never tried it?
That being said, I'm really attracted to women right now, giving preference to cis-women, although I do find some trans-women very attractive. Men just seem "blah" right now. In my mind they're just smelly, hairy children trapped in an adult bodies with penises, only interested in one thing. I've had to deal with my share of "->-bleeped-<-s", can you tell?

I currently have a cis-girlfriend, and we got together right around the same time I started my HRT. She's the first relationship I've had since coming out and so far it's been quite a ride. Interestingly enough my GF does not consider herself a lesbian, but knowing some of her experiences, I classify her as Pansexual, much like myself.
She often comments on how she doesn't want me to "cut off my parts" and is worried I'm going to start liking men. But, we have great fun together just being women and doing the things women enjoy... shopping, cuddling, cooking and even crying together. We have an active sex life, with her being the "top" about 90% of the time and also the dominant one in the relationship (she calls herself the bossy girlfriend)!
The serious role reversal has blown my mind! She craves sex, waaaay more than me, to the point where she can get frustrated when I'm not in the mood. I need some romance and tenderness most of the time before I can even get started. It's been such a shift from what I've known as living as a guy before my coming out and transition.
Sorry for the long backstory, but to get to the OP's original question:
The interesting thing, I do catch myself fantasizing about having a relationship with a kind, caring man who's totally in love with me. It's the ultimate straight woman's fantasy, I suppose!
I hear a love song on the radio (usually a guy singing about an ex or current lover), and I think "OMG, I so want to be the woman that guy is pining over and wrote the song for"
I really love the self discovery this transition ride has provided me.
...and oh the TEARS!