I run Top Hat on a Kobo e-reader; i.e., gray scale. Very legible. As good as my old Compaq Aero but a much larger display.

I also have a Dell Streak 5 in the pocket as a backup, which I was forced to go to at Cordele this summer when the Kobo stopped getting GPS data from my PowerFLARM. I much prefer the color (Dell)...but it's not nearly as readable. It's "good enough". So if I could get a more readable color display at comparable or even moderately higher cost, I'd go with that.

I like having a completely independent backup, though (self contained battery, GPS, CPU, display), so I'll probably keep the Dell Streak in the cockpit for a long time.

Chip Bearden