To me, I don't see folks as FtM or MtF or anything like that. A lady is a lady if she says so, and a gent is a gent if he says so. And if you're neither/something in between/both/etc? I'll roll with it and do my best to be a supportive partner.
What matters to me is how I interact and get along with someone, not what's between their legs. If I can find someone to be happy with and find a great friend in, then I'm cool with them. Granted, if I were to date a trans lady(or even a cis guy), I would probably feel very envious of what they have and it might strain the relationship/make anything sexual damn near impossible, but if I cared enough about that person and they me, things might turn out alright.