My philosophy here is this:
I might not tell before the first date, or on, or even in the first few dates. I will however tell before I am intimate with my partner, pre-op or post-op.
I'm sorry, but every human has a right to be selfish on what they want and are attracted to. We don't owe anyone our attractions, and no one owes us theirs. There are people out there for which being trans is not a deal breaker, and there are people for which it is. How would you feel if the situation was reversed. We all have things that are deal breakers, and how would you feel if a deal breaker for you was kept from you and your partner spent years actively lying to you about it?
I'm not condemning anyone for doing things differently, this is just my opinion. But I can't be with someone in a committed relationship and keep this huge burdensome secret secret.
I've done that for the last 30 years, and it was full out killing me. I'm not going to go around and tell everyone I'm trans, I'm not going to broadcast it, I'm not even going to tell most dates. Because a date is just a date, it's a pre-cursor to a relationship. I will however tell anyone that I am interested in a true relationship with. And I will not sleep with anyone without being up front about it. Too often this is a cause of violence against us. The discovery that they unknowingly slept with a transwoman, and too often it ends badly. One such case I heard about recently after a husband learned after 20 years of marriage his wife was trans. His rage and assault was fueled by the deceit more than her status as trans. Furthermore, this just seems to me to be perpetrating the idea that trans* people are out to "trick" unwilling people. It's not what we're doing, but a lot of people out there do think this.
Maybe my attitude will change one day and I'll be tired of disclosing. But I still think I'll tell before intimacy and anyone who I want a relationship with.