I will never buy an eReader without support for koreader. It's absolutely essential to me, most importantly:
* Lots of quick fixes for poorly chosen CSS properties (called "style tweaks" in koreader), just apply them on-the-fly.
* Support for StarDict dictionaries, which you'll find plenty for all kinds of languages.
* Great PDF support with automatic or manual cropping, and special viewing mode for two columns, perfect for scientific papers.
* OPDS support so than I can easily download books from my Calibre library
* On Kobo, way, way more options to set the backlight (original firmware is way too bright in the dark even on lowest setting), many options to configure "warmth" of the backlight for late-night reading
* Great support for bookmarks
* Super easy to hack and contribute as almost everything is written in Lua
* Lots of quick fixes for poorly chosen CSS properties (called "style tweaks" in koreader), just apply them on-the-fly.
* Support for StarDict dictionaries, which you'll find plenty for all kinds of languages.
* Great PDF support with automatic or manual cropping, and special viewing mode for two columns, perfect for scientific papers.
* OPDS support so than I can easily download books from my Calibre library
* On Kobo, way, way more options to set the backlight (original firmware is way too bright in the dark even on lowest setting), many options to configure "warmth" of the backlight for late-night reading
* Great support for bookmarks
* Super easy to hack and contribute as almost everything is written in Lua