One on hand they provide a handy means of picking up high signs and reading a routesheet in the dark. On the other hand they can be distracting for drivers and fucking annoying for anyone riding with you if you turn your head unexpectedly.
I prefer a handlebar mounted light and occasional use of a finger light if I'm going to be picking through a bitty route in the dark.
Opinion is divided.
One on hand they provide a handy means of picking up high signs and reading a routesheet in the dark. On the other hand they can be distracting for drivers and fucking annoying for anyone riding with you if you turn your head unexpectedly.
I prefer a handlebar mounted light and occasional use of a finger light if I'm going to be picking through a bitty route in the dark.