I'm really sorry my job only lets me follow AMC on FORT these days--so I can't really have an opinion on how good a job they are doing with this. I'm very curious about it. I agree with Critical and nilesgirl on this, Uncle David--sexual orientation and gender identity seem to be two completely separate things so far as we can tell, that just are often paired in a certain way for maybe 90% of people. But they don't have to be.
Just to give you another headscratcher, I remember a NY Times story a few years ago about a lesbian boarding school couple, one a senior, one a junior in high school. The senior went to college (Harvard, so the story was about how Harvard handled this housing-wise) and over the summer between high school and college came out as trans, and moved into a male role. He was still involved with his high school girlfriend however. Now, does that mean the high school girlfriend is suddenly not lesbian, but bisexual? Or straight? Obviously our language doesn't really deal well with this stuff--probably because only recently have we started to talk about it.
Another example--there's a middle-aged returning student at my college who publishes in a campus poetry journal as a lesbian--but X is a biological male, happily married to a woman, and looks and dresses basically like a truck driver, complete with full beard--the only "feminine" adornment normally is a kind of pirate earring. However now and then X dresses like a traditional woman, keeping the beard though. X gets pretty much all A's and pays tuition from cans collected around campus so as not to cut into their normal lifestyle--a real original! So do we call X's wife a lesbian?
Just so you aren't alone though, Uncle David, there's a women's music festival in the Midwest that only admits women. It's a kind of Woodstocky event with a lot of toplessness, etc., and they want to keep it all female. There has been a running argument over admitting people who were not "born women," and this among people who are very activist in LGBTIQ issues. So clearly not a "right" answer yet.