It is the time of year again (fall/winter) when it's still dark during part of the ride in the early AM or after sunset. It would be nice if the Edge 840 had an Auto Backlight option that is triggered when the ambient light falls below a certain threshold. It would also turn on when you're riding through a tunnel, highway underpass or heavily wooded area. Right now, the backlight option is hidden in too many submenus that are hard to navigate to turn it on, and then off again, and an auto backlight option would be so much more user friendly.
My rear bike light works like this (Magicshine Seeme 200) and I've found it to be very useful. Wish that Garmin would have it as well. Thanks!