Well, in my case, I am not at the point where I can't do everything I can to appear as female on the outside as I am on the inside. So, here are my thoughts.
I have only gotten one ma'am and that was a couple weeks ago. Prior to that I got a confused "sir or oh I mean ma'am". This was just after I introduced a wig so that I could have long hair while I am in public as Amy. Prior to that, I never have gotten a "ma'am". Always "sir". Lately, I have gotten no "sir" or "ma'am".
One time I had a fortune in a fortune cookie that stated something like, "Be simple in your dress." Well, I noticed that is some good advice. When I try to over do it, I stick out more. However, if I keep it simple, I am more relaxed and confident and people respond better.
I usually have no issues while in public. Out in public for me was the first place I could be myself because at home or anywhere else were off limits. Now that I have been living on my own, things have improved and I am myself all the time except at work.
Anyway, back onto the strict topic of a man in a dress. This question is being asked to a group of TG people who don't feel that they are men in dresses. So, in my opinion, I have to think of it as a "male" in a dress these days.
Prior to accepting the fact that I am female already (at least on the inside) rather than just wanting to be female, I tried the "man in a dress" thing as a way to cope with my gender issues. I figured that if I could be happy as a man in a dress, then I would not have to become a woman in a dress. That didn't work so I am now beginning to become that woman. But, during the man in a dress days, it was always "sir".
Like I said, it was the addition of a wig that significantly reduced the number of "sirs".
So to sum things up, just wearing girls clothes without no other efforts and you in your mind see yourself as a guy, then you will get called sir.
Amy