In the interest of full disclosure here, I'd say that slightly less than half of my RPG characters have been female. My AD&D monk of Cressa who I played in college is still a favorite character of mine. I don't randomly roll character gender. I typically pick a couple class/job/professions I'd like to play this time and toss them into the bubbling mixture of ideas in my mental cauldron.
However, I have noticed that one or two people in our group (all of whom are male) seem slightly uncomfortable with a male playing a female character. One seemed to be inclined to let it pass on the basis it was determined randomly and thus not a conscious choice. Others seem to wonder why a male would want to play a female character, not in the sense that it suggests that person subconsciously wants to be a woman or is "some kind of faggot", but in that it seems like a lesser alternative somehow. Sort of like: why would you buy a SmartCar when you could have an Escalade?
Of course, in modern RPGs there are no arbitrary limits on characters due to gender. I seem to recall AD&D having limits on maximum strength for female characters. Depending on the campaign setting there might be some "cultural" limits on the roles of female characters. Drow elf culture, for instance, puts females in the role of clerics and leaders. But I rarely see gender discrimination built into the rules. There is a lot of stupid cheesecake art out there, like female paladins in ridiculous bikini plate armor with garter straps, but that's not part of the mechanics.
So does anyone in your games randomly roll for character gender?