Not (very) applicable if you have a strong gender identity: I'd always been fairly confused as to whether I was a woman or a man, neither one really fit quite right. Five years ago I met my first person who identified as genderqueer, but generalizing from that (one) example I thought it a mere label - I didn't see how their behavior diverged substantially from their sex given gender. Last year or so, The Third Alternative, Keeping Your Identity Small, and applying being a linguistic descriptivist to my broader life came together. I'm a person, more or less human, and that's it. One can choose null (but of course, the vast majority of acquaintances won't notice...).