Way back on June 3, my mother asked if we had mirrors. Both Scott and I ride with mirrors. I have a bike mounted mirror and Scott has a helmet mount. When I see him with helmet and mirror he reminds me of the borg!
I really like my helmet-mount mirror. Early on I had trouble focussing on it, since I seem to be right-eye dominant, and I look at the mirror with my left eye, but I seem to have retrained my brain without too much trouble. With the mirror appropriately adjusted, I can see cars coming from a distance in my peripheral vision, and check across multiple lanes of traffic with a slight turn of my head.
A few times when I’m off the bike, I have noticed myself trying to use the mirror to see something behind me. Unfortunately, without the mirror I have to turn around instead!