Zutilo's usage statistics are public on its AMO page
It would be great to get French and German because the next three most popular locales after en-us are fr, de, and de-de with around 100, 70, and 60 users respectively. I hope that with translations for those locales that the numbers would grow larger. It would also be good to get a Spanish translation because es-es, es-mx, and es-ar together have about 50 users. Other locales would also be great (maybe the usage numbers would grow after the appropriate locale existed), but those are the languages with regularly more than 50 users.
I started to review the German translations. Saving works now! The first half of the Readme is now reviewed and refined.
The locale files are both fully reviewed by me.
There is one issue with the term "Eintragsmenü" that should be synced and checked against the Zotero translation memory (that may not exitst ;-).
Hope I can finish the Readme soon.