Gromit, "genderqueer" is not a slur; it is the "Q" in LGBTQ. It refers to several forms of self-identity:
http://en.wikipedia.org/wiki/Genderqueer
It's something of an ambiguous/catch-all term for people who don't quite feel that they fall under "straight", "gay", or "trans". For instance, my ex-JW friend identifies as "genderqueer" rather than "lesbian"...she is attracted to women and uses the pronoun "she" to refer to herself, but told me she has always felt more male than female, and considers herself sort of both male/female. To my knowledge, she does not want gender reassignment surgery but is happy as she is. I asked her how she prefer I refer to her, and she is the one who introduced me to the term "genderqueer". So that's what I do.
It's not considered an offensive term in the LGBTQ community, versus slurs like "tr*nny", which are considered highly offensive if used by a cisgender person...The term "trans person" is the preferred technical term, I'm told.