A must have! Rated 5 out of 5 stars

Thanks for your great work. It really makes my web experience pleasant.
The need to open a new tab or even move away from the parent page JUST to view an image is stupid & does get annoying after a while. This takes care of all tht! :D
The only complaint would be the missing "save as" icon on the enlarged image. It would make those thumbnails more interactive and the add-on perfect!

This review is for a previous version of the add-on (1.6.0). 

Save Enlarged Image As...

In the current release (1.6.0) you can right-click on the thumbnail and do "Save Enlarged Image As..." to save the full-size image. I expect the next beta release to also include a hotkey ('s') for this.