Ever since crossing wheels with the cyclist in front of me when I was looking back to see if traffic was clear to cross a major road, I've used a Take-a-Look mirror clipped to my sunglasses so I don't have to take my eyes off the road in front of me. When I first started using a mirror, all the wrap-around sunglasses had weird shaped returns that the mirror would not stay in place on. The mirror would always twist of just fall-off.
This caused me to try other mirror configurations (bar-end and helmet-mount), but I kept coming back to the eye-glass mount despite the problems because it placed the mirror in the best position.
When I discovered the Smith Pivlock glasses, I was thrilled. Finally, a nice pair of glasses that fit well that had a tall, narrow temple return that the mirror clipped onto perfectly and stayed in place.
So, what about the glasses. Even without considering the mirror compatibility, the Pivlock's are great. The nose piece is adjustable and doesn't slide down. I have pretty heavy brows, and the lenses stay far enough off my face to not interfere, and to stay fog free on foggy mornings. The lenses can be fairly easily changed, but I've now got two pair (one with clear lenses for night-time commuting) so I don't have to change them often.