Not like I have a choice when I'm really in love.
But still hard to answer without being in the same situation. Sometimes you can surprise yourself with your actions.

Well, I'd never get into that situation in reality. I've never seen a man to woman transformation that I couldn't spot. I'm an extremely observant person when it comes to features, expressions and habits. Women have many subtle cues beyond boobs, pussy and (lack of) body hair that say they're a woman. Eye shape, jaw shape, hips, shoulder ratio, arm motion, Adam's apple (obviously), leg motion, smell... ways of communicating, expressions... they are all distinct and consistent to women and I've never seen a man copy it accurately, regardless of surgery or hormones. Even if in a photo it can be masked, in person it's obvious. A true give away is voice, as a woman's voice is processed by the areas of a man's brain that processes music while a man's voice is understood by the part that handles math. It doesn't matter if it's a high pitched man or low pitched woman.

However, if I were to suspend reality and say that I could be fooled by presentation, I would politely leave the situation. The simple reality is that I want a woman. I want to have kids and a family. The idea of being with a man sexually is gross to me, even if they look like a woman. I would never be able to forget that they were (are?) a man. And I find the idea of surgically messing up a perfectly fine cock to make it look like a vagina seems mentally unhealthy to me, and it won't actually be a real vagina anyway. I'm OK with elective surgery, and I think people should be free to express themselves as their heart desires, but altering your genitalia to make it look like the opposite sex and taking synthetic hormones seems to cross a line of good health for me. I feel someone considering it should be encouraged to be comfortable in their own skin rather than trying to change it.

Well, I live down the street from Sony's studios does that count? 

Break up with him and if he was lucky I wouldn't kick his butt. I would also tell him he is a ugly person in and out.

Before someone jumps on me. If someone is going to waste my time and lie to basically he deserves no respect. If you want to be a fake person and get yourself in situation where you don't care about disrespecting / hurting someone. Don't be suripised by the results. I feel no emthpy for people like that.

Also, not being honest is a deal-breaker for me and this is something he should have been upfront about. "Weak" isn't a good excuse for me. If you're someone who would be weak about this, you would be weak about other things, and clearly we are not soul mates.

Leave.

Physical attraction is necessary for a relationship, and both the ability to have vaginal intercourse and the ability to have children are on my essential list of qualities.

Assuming the surgery is so perfect that these things are possible, I don't object in principle to the person having been male in the past.

Story Time!

This sort of happened to a friend of mine.  She was dating this guy and pestered him into proposing marriage.  She was in a huge rush, and wanted to marry on the anniversary of their first date.  She was also desperate to have kids - and offered to have them for me and my boyfriend (which was a totally weird conversation that came out of nowhere.)

I like him ok, and I was one of the few of her friends that he actually liked, but felt something was amiss.  One day I pulled her alone, and said, "There is something he is hiding from you.  You don't need to rush to get married, why don't you keep dating for a while?"  Well, that didn't go over so well, but I think it's what you should do as a true friend.  Turns out a couple of other friends did similar things but for different reasons (like what I learned was his violent/rage temper.)

Anyway, they got married and she was kinda nasty homophobic to me.  I wasn't allowed to bring the person I was dating, but a mutual friend was allowed to bring here date, even though I had been dating longer.  It ended up being rather hurtful and mean on her part and eventually led to the end of our friendship (along with a bunch of other things.)

So I lost touch with her.  A friend send me something a while ago, and well, turns out he was hiding something rather big.  He didn’t want to be a he, and is now a she.  My friend is not a lesbian.  So I’m not sure how they are working it out as they have two kids.

TL/DR: Girl marry guys.  Girl isn’t very attractive (inside or out), guy get’s penis removed so he never has to stick it in her again.

That... is quite the tale. But that's almost karma for your ex-friend, for being very mean with you considering the values of friendship :/

I don't really see myself in this situation, like thelaststarfighter said there are many many things that make it easy to see the difference between a man and a woman, I even have met guys who claim to be a woman trapped in a men's body and by the simple behavior I can always tell they are men, besides I also live in a poor country so the chances of meeting someone who has enough money for a total body reconstruction are practically nonexistent lol.

but let's say it does happen... I think I would simply leave politely because I like women, and I don't see myself with such strong feelings to overcome that, a revelation like that would simply destroy any feelings that existed and would make me look elsewhere

Yes, yes it is.  She ended up doing many bad things.

I felt actually affirmed that I new something was up.  Like when I figured out Ted Haggard (anti-gay mega church preach caught having an affair with a dude) was lying.  I felt like he was telling the truth, but knew he was lying.  I just wanted him over and over until I spotted his tell.  It was a neat moment.

Fun Fact: My parents never liked her.

Also, I have met some transgendered people.  And many you wouldn’t know unless they tell you.  For me it’s like overweight person getting weight loss surgery.  I don’t get it, but it’s not my battle and not my place to judge.

PS What about Bruce Jenner? (1976 US Gold Metal Decathalon winner.)