Maybe I'm just too old and cranky, but I could never use they, their or them as a singular pronoun. And as for the he or she or he/she construction, that can force us into abominations such as: "If he or she doesn't pay his or her taxes, the IRS will come after him or her." PC or no PC, I have to go with the masculine forms continuing to be used when gender is irrelevant, as has been the tradition. I wouldn't care if someone used the feminine pronouns instead. I've noticed that some high-school textbooks have made a point of alternating from chapter to chapter. Maybe a bit labored, but no real harm done.