To repeat what many others already wrote :
* Show time next to battery
* Change battery icon to a simple pourcentage
* Add a french dictionnary
* Add the number of page remaining in the chapter (in addition to the global pagination already there)
* Add annotation for sideloaded epubs
* Autocrop white border from image loaded from cbz or cbr
* Add an OPDS client (to be able to browse through Feedbooks.com free books or custom OPDS feed), not sure Kobo is gonna do this one
But beside all that I'm pretty happy with my Kobo.