I can recommend the
Russified firmware for the 350/650, unless you are Dutch (it replaces the Dutch language with Russian).
Although it is called "Russified" it is really suitable for anyone--it supports the same languages (except Dutch) as the original firmware, on which it is based. It has lots of cool features (and more being added); the ones I like the most are:
Clock always visible
Can use Zoom and Options buttons as previous page/next page.
Global css support for epubs (e.g., so you can override the fonts used in an epub, without having to edit the epub).
Disclaimer: as always, flashing your device with new firmware is at your own risk!