A server at a sandwich shop in Oxford called me "ma'am" and the guy I was with was offended on my behalf, but I told him I was pleased -- 'cause I look younger than I am and have always been a fan of being older. "Miss" doesn't especially ping me, though, provided the tone it's said in is neutral. I do wish there were an age-neutral designation for females, though (like the marriage-neutral "Ms.").

Your example of being a service provider at the Store makes sense. (Though I would be inclined to use the more-leeway-granting script for _everyone_.)

You fear men? I guess I shouldn't be surprised, but I always am when I hear this from people.

I personally tend to avoid servicepeople because I usually know what I want and where/how to get it and don't want to be pushed into buying/selecting stuff (this is mostly true at clothing stores).