The monochrome LCD doesn't use a lot of power, though, being used in low power devices like watches. Nikon cameras are displaying the number of shots left on the card, even with the camera off.
And how about reliability? I know cases on which e-book readers had their display broken, because of the lower pressures during a flight.
What I think it could be advantageous, is the freedom to display the information (compared to the fixed format imposed by the monochrome LCD). Adding colour could be possible, too, for an even more informative display. I'm not sure if we really need it, but it could be worth giving it a thought.
By the way, Ricoh is actively developing such technologies:
Bright, full color e-paper under development by Ricoh - DigInfo TV