I prefer Ms or Miss and don't think I would mind Miss even if I was married. Mrs annoys me because it is ASSUMING that since I am the age I am, I am married...and Ma'am just sounds ugly and makes me agitated.
At our one department store where they are trained to be obnoxiously friendly they have pretty much given up on calling me Honorific + my last name (because it's unusual and some people have a hard time with it) and just use my first name. Seeing as I'm there more than at some of my relatives' houses that's cool with me.
