Most of the stuff mentioned here wouldn’t be a deal-breaker for me – I think the only things that would are a history of domestic abuse (i.e., not just one incident) and/or a history of child or animal abuse.
Former drug use, alcoholism, sex industry employment, prostitute use, felony convictions, etc. either wouldn’t matter at all, or wouldn’t matter enough to make me call things off. Ok, a collection of felony convictions might, but I’d listen to his story first.
The only thing I’m sort of on the fence about is a sex-change operation. Reading this thread is kind of funny timing for me: I’m right at the start of what could be a very nice relationship, and so far there are no red (or even yellow) flags – for either of us. We’ve started joking about it, actually, with each of us saying that there has to be something wrong with the other, and I’ve been thinking about outrageous things I can suggest the next time it comes up: I figure that accusing him of formerly being a woman would get a good laugh out of him. But then I started to think, “What if I say that as a joke but it turns out that he was? Would it be a problem?” I have a long history in the LGBT community, so I don’t think it would matter, but I can’t honestly say for sure. I know that he’s dressed in drag before (as a Rocky Horror cast member) and that doesn’t bother me – in fact, I like that about him – but actually having been a woman? We haven’t had sex yet, so I’d probably ask for demonstration before making a decision. 
