If you have an Android device you can now install the app and find out important things like the battery degradation.
The app is no longer in beta testing and now costs 9,90 €.
Now it will be easier to test the reliability of the more recent LEV50N cells. If your i-MiEV, C-Zero or iOn was built after the 2012 summer you might be lucky enough to have them.
Feel free to share your battery data in the comment section.