I may be able to finally contribute something useful to a discussion.....

I've had an Edge 800 since last October. I often ride in the very early morning hours (I'm talking 4 or 5 am). With no light you need the backlight to see anything. I have the 800 set up to go dim after two minutes. A simple tap on the screen brings on the backlight and everything is very clear. During the day, the screen is VERY readable and I don't worry about the backlight at all. I'm very happy with the unit and highly reccomend it to anyone who asks.