As far as a usb light is concerned, it only narrowly misses my point. I started out thinking wibni the keys were either all lit, or programmable so that certain of the most useful ones might be. Then it occurred to me that being able to locate them quickly without actually looking at them would be better yet. The only reason I might have my hands on the keyboard while in a moving vehicle is for making adjustments to the map. I am not going to be planing routes, proofreading notes for an upcoming meeting, or emailing.
With those keys that are req'd for zooming in and out, dimming/brightening the screen, and map scrolling easily identifiable by touch, I don't need to look at the keyboard and hunt for keys night OR day. Despite my disclaimer above about safety while driving with map software activated, I must say that using the keyboard for anything (plannng routes or writing emails for instance) more than adjustments really ought to be done pulled over somewhere, or by the copilot.
A usb keyboard illuminator is really not much improvement on this. Heck, in a pinch I could just angle myscreen down a bit or hit the dome light if all I needed was visibility in the dark.