I use the end mounted drop bar type-- I can at least see the color of the F150 that is squeezing me into the shoulder!

I like to use a mirror for the security it provides ev3n though the image is shakey. I once viewed an approaching vehicle that was taking up the entire mirror-I pulled off the road and stopped to let the house mover continue on his way unobstructed by a mere cyclist--there was no warning and no advance vehicle. Just a house traveling at 40mph taking up the whole road.