As an experienced writer I'm too good at gaming these.  If I were to dump a writing sample from one of my stories in, it'll give me the gender of my narrator, which usually isn't me.  If I dump a writing sample from my Facebook though it usually rates me as female, but barely.  Probably because I have an extremely large vocabulary and am not shy about using all of it, regardless how my word choice might be interpreted gender-wise.  Makes me difficult to gender in conversation based on word choice alone, but it does tend to make me come across as "stuffy" or "stuck-up" even though I'm really not.