If by myself it's not so bad without but in a group or in town I have to have a helmet mirror, too many sounds to keep track of and no time to turn and look behind. On motorcycle I have a bar-end mirror, gets it out far enough that I can see behind me instead of whats of to my left and what i'm wearing.
If you think a helmet mirror looks bad think about how bad a case of road rash looks.
my 2 cents