Rated 4 out of 5 stars

This addon is almost perfect. The only thing I can think of that would make it even better is a button to switch to private browsing mode that could be placed in the addon bar or nagivation bar.

This review is for a previous version of the add-on (0.1.1.1-signed). 

Good suggestion! Keep in mind that soon, Firefox will have per-window private browsing, so that button may not be as useful anymore.