We have one guy in our group who rolls to see which gender most characters will be. Can't say it really makes a huge difference in-game, other than I occasionally have to correct myself: "So you're going across town with him... er, I mean her. Damn."
I don't like to RP female characters as a PC myself simply because as a male I don't feel like I have enough of a grasp on the female mentality to accurately RP one, so I just leave it. I got no problem with others who do it as long as things stay PG-13 territory.
As a DM I have noticed I tend to gloss over female speaking parts or where a female NPC will give information. I do alot of "speaking voice" type stuff for male NPCs; I guess it really just relates back to what I am comfortable with RPing (talking about RP-skill comfort here.)
Our group is all-male, if that matters. My wife did play with us a few years ago off and on, and she never saw anything weird about it either, in case a woman's point of view would be helpful. On the flip side she has never indicated she wanted to play a male hero, so maybe she is inclined to stay in-gender for her RPing also. I'll have to ask.