What does this even mean? There is no one "women's personality" or "men's personality". The range of individual personalities is wayyy broader than whatever statistical difference may exist between the sexes. No matter how "manly" you act, there are plenty of real-life women who act that way -- and I'd wager that many of them, if you met them, you would not even find remarkably tomboyish. So my advice is not to sweat it. Just play your character as you imagine him or her.
Fun fact: Ripley in Alien was written with no first name or defined gender in the original script. Cast Sigourney Weaver, and all of a sudden people are writing analyses about how the film allegorizes the contrast between female (Ripley) and male (xenomorph) sexuality and all other manner of gender-based navel-gazing. There's not that big a difference between men and women -- it's just that people see women and then look for a difference.
Hrm, let's see if I can do this without starting a fight.
I've seen far, far too many elf characters where it was entirely impossible, without looking at the character sheet, to know that this character is an elf. I've been in groups where one player turns to the other player and says, "What do you mean you can see in the dark? You're an elf? Since when?". To me, this is a failure (I'm not saying it's a failure to everyone, just me) in role play in that the player in question has not presented his or her character in such a way that the other people at the table have an accurate picture of the character in their minds. Granted, it might be a failing in others, true, but, I've seen it happen fairly often that elves get played as "Humans with pointy ears". The fact that they are virtually immortal, non-humans just never comes out in the portrayal. And I really don't like it.
If my female character acts exactly the same way as my male characters, to the point where no outside observer would have any idea that my character wasn't male, then what's the point of playing a female character? For me, role playing (and again, I'm not badwrongfunning here, I'm talking about what I enjoy) is about the portrayal of the character. For me, success is when the other players at the table refer to me by my character's name and act and react according to the character I've portrayed, not me, personally.
And, to be 100% honest, I've never really been sure how to pull it off with a female character. I'm afraid that my female characters would either be "just another dude" or would come off as too stereotypical. Like I said, it's my failing. To respond to your last point, my fear would be that people would look at my character and not see a woman at all. Which, again for me, makes me think, "what was the point of gender bending?"
Still in the vein of full disclosure, I bring this attitude to all facets of my character. If my character is from a particular group of people/culture, whether fantasy or real, I really try to make that a visible part of my characters. In an old GURPS game, I was a black scientist from Nigeria on a mission to Mars, and I did a bit of homework and brought Nigerian culture points to the table during play. Food he chose to eat, methods of dress, culture references, that sort of thing. It wasn't the only facet of this character, nor even a major element of the character, but, I know that everyone at the table had a pretty good mental picture of my character when we were playing.
And to me, that's successful roleplaying.
((wow, how many times did I just repeat "to me" in a single post. LOL

))