There was one point where a new player in our group said it was really weird that another person, a guy, was playing a girl. I pointed out, "Your playing a giant cow that stands up right." (minotaur).
And while it doesn't apply to D&D, in video games, he usually plays females as well because "If I'm going to be sitting here staring at a screen for hours, I want to look at something pretty."
But yeah, gender doesn't mean much really. If your out there throwing balls of fire, summoning demons of the abyss, fighting darkmantles, walking corpses, and dragons, why are you concerned if someone is playing a gender that isn't their own? Its all pretend ^^