Works great! Rated 4 out of 5 stars

Great idea! :-)

I second the suggestion to add the option to choose the number of displayed months and also the starting month.

Another thing would be lokalization. Is there a way for me as an extension-user to change the text appearing in the tab from "year" to e.g. the German equivalent "Jahr"?

I, too, hope that this will be added to the TB-core!

This review is for a previous version of the add-on (0.3.0b2). 

localization

download the .xpi, rename it .zip, open it, extract the folder chrome/locale/en_US, translate text values in calendaryearview.dtd and calendaryearview.properties and send me those files :)