In addition to so many great suggestions above:
1. Ability to organize the Archives - mine are becoming way too unwieldy.
1a. Ability to sort Archives by "Most Recently purchased", so we don't have to hunt through 20 screens to find the latest books bought and sent to another device.
2. Better caulking between the screen and frame. (Stronger and less grooved, to avoid lifting and pet hair intrusions.

)
3. A single button for TTS on/off
4. Raise the 5 way's edges so it's easier to use without hitting other buttons.
5. A "Favorites" sub-menu from the main menu, so you can flip between books or documents.