I currently use a melmet mirror, and I'm completely used to it by now. In fact, when I hear something behind me while I'm walking, I often turn my head 180 degrees from the sound, in order to get a mirror view! It's actually become a reflex reaction now.
I'm currently looking at new helmets, since I need one for summer that has bigger vents, and just looks better. Most of the newer helmets don't have a good place to mount my helmet mirror! I may have to rethink the whole mirror thing for my roadbike.
I don't like bar mirrors-they always break. The hood mirrors seem to be in the way, especially for somebody who uses the hoods a lot. I'm seriousl considering a top-tube mirror, but I've never used one before.
Does anybody out there have experience with one? Seems to me, your thighs and crotch will be most of what you will see in this type of mirror. Is is practical for seeing traffic? My recent near-hood-ornament experience leads me to believe that seeing homicidal motorists before they run you over is the most effective method of preventing injury.