What's the big deal about it all?
It's so simple, no need for any further discussion.
With my neighboors, teachers at school and women I know who are married I've always used Mrs.
As for women I don't know I always stick to Ms. and have never had a problem. I don't think it sounds impolite.
Young girls I just call by the first name.
As for Miss...I don't use it that much. I remember using it a few times in school because I had some single teachers.
Concluding, I think titles are a part of an old society. I don't think that calling a person by his/her first name shows disrespect at all. My mother for instance prefers to be called by her first name and all of my friends do so. Besides, I also call many of my friends' mothers by their first names and we all have a good relationship.
Let's evolve our minds, we're in the 21st century.