Stuff which may be above the kindle stock features (as seen on Paperwhite 10):

- Allowing to highlight text across pages. Used to work in the past but no longer works

- Allowing exit to library from mobi files without a cold reboot of the device. Used to work, no longer works.

- Not deleting contents of my library on an update overnight? (files still on disk, metadata gone, no longer visible on Kindle)

- consistently working dictionary, offline, at least for English texts? (used to mostly work, with recent updates it is broken)

- Not getting worse on every update

- Better keyboard layout, maybe supporting smaller languages

- Not deleting purchased books remotely

- better bookmarks and navigation support. I find Kindle useless for the technical reading and learning materials, as navigation and cross-referencing is slow clunky and useless, I need paper books for that, or a computer.

- Better image display? Also hinders proper use for digesting technical content.

- Text Search?

- EPUB support.