mirrors definitely have a place on road bikes. I have the "Italian Road Bike Mirror" on my commuter and race bike. It goes over the end of the drop bars and you tape in on once you get the angle right, then grip tape over the top. it is optical quality glass and not much more diameter than the bar end. obvious advantages for commuting, plus at over 20 mph I can't hear that much over the wind noise. For racing as nerdy as it sounds you can stay aero and still see if anyone else is gaining on you. I have used it to my advantage many times when launching an early sprint. I would also say a mirror enhances safety bc you don't need to turn your head, just a quick glance down and your eyes can be right back where they need to be.