I'd like to think I'm open minded, but I wouldn't know unless I was in that scenario.
There are a few problems however.
1, If I was aware of their transition, I'm not confident I would see past that. Again, I'd like to think I'm open minded, but I have had no experience engaging with a transsexual (that I'm aware of) and can't say how I would react to that knowledge.
2, I'd prefer to know in advance... this is pretty much a catch 22 for the individual I'm courting. If they don't tell me right away this could create a problem in the future if we are still together. But if they did tell me we would be back to the first problem. One could say I could be kept in complete ignorance of the fact, but there are a few scenarios where the truth can slip. Dealing with their family and planning a family as examples. This would create a double whammy effect (betrayal of trust and coming to terms with that bomb of a revelation) and I'd seriously question the viability of a relationship in that situation.
Finally, I have a slight issue with surgical modification. It's mostly irrational, but I can't shake it... I have a strong preference for naturals. This isn't just against transgendered individuals, but everyone. Heck, it doesn't even have to be surgical, I find a lot of cosmetic "improvements" towards women off putting. Hair dye (within reason), Nail Varnish and fake nails (I just think it looks tacky), Eye Liner (its face painting), Shaved pits and pubic regions... It's weird that we are living in a world where attraction to a completely natural form is considered fetishistic.
I'm NOT totally intolerant to these things, but to the extend and frequency that most girls I know use them, I have issues. It betrays more self confidence issues then it hides superficial flaws.
In short I have a strong preference for Au Naturales.