Part of my ride is on a really busy four-lane 55mph+ road, and I've been thinking more and more about my own safety. I have a pretty wide shoulder for most of it and generally feel ok about the ride, but all the cell phone use, texting, and other driver distractions has me wondering a bit. So I'm thinking about getting a mirror. My question is, do you think a mirror really makes you safer? Will the extra half second get you out of the way of an oncoming car, or is the mirror itself just another distraction?

Also, if you use one, what kind do you prefer? The bike mounted kind, or the kind that clips to your glasses?