I'm a little surprised that people are going on about 'why should gender be important', etc.
I agree that the option of publicly displaying your gender if someone chooses to is a good idea. It's not just about using gender neutral comments, but if someone is talking about, say their relationship with someone, knowing that you are talking to a man or a woman, can help with giving advice. I don't think I would want to PM someone or ask what gender they are, I'd feel a little awkward. I've actually had to ask someone before if they were a man or woman and it didn't go down well.
I mean if we have the option of sharing our disorders on our profiles, or showing what country we're from, or how many posts we've made, then hey, the option of showing gender fits right in.