1. tags, leading to virtual folders. Also a way to customize your virtual folders, e.g.
Author | Series | individual books or
Genre | Author | individual books or ...
2. After switch on -> return to page last read
3. List view in library, with options to sort on "last recently read" and sort on "Rating" and "Purchase Date". This would also mean that there should be a way to rate books
4. Remappable buttons
5. Reading while charging
Customizing your virtual tag folders doesn't need to be anything fancy; I don't mind if this would be a power-user option, having to edit an ini-file in the System folder or something. Furthermore, I would propose to use the tag infrastructure already used by Mobipocket; it is already there and can be maintained by using the Mobipocket Reader. Maybe not ideal, but sometimes you have to be practical