Rated 5 out of 5 stars

Great add-on! But it doesn't seem to be working with the new Tumblr format on their 'archive' pages.

This review is for a previous version of the add-on (2.4.3.1-signed). 

This is fixed in version 2.4beta1. https://addons.mozilla.org/en-US/firefox/addon/thumbnail-zoom-plus/versions/