I've never "relied" on mirrors. I always look over my shoulder.
I like riding with them, especially when commuting, as I always have a constant awareness of the situation behind me, which enables me to adjust my speed so that when I get to a junction I want to turn right into I have aligned myself with a gap, which just needs a shoulder check to confirm.
I don't have mirrors on any other bike, other than the windcheetah, and although I do miss the total awareness of my surroundings I don't have a problem riding, nor do I need a distinct need to go out and purchase more mirrors.