john smith wrote:
Larger screens, color screens.

Color is not a good choice until a better, longer lasting, portable
power supply is developed (or a lower powered, less demanding color
display is developed.)

The new Garmin 60c & 60cs hiking/driving units with color screens use less
power than any of their previous handhelds with grey-scale displays. The
specification is 30 hours of use on a pair of alkaline AA cells and
indications are this is achievable under daytime outdoor conditions (where
the transreflective screen doesn't need the backlight).