Rated 5 out of 5 stars

very useful for me... but could you make private tab button beside newtab button, instead in addon bar... thank you

This review is for a previous version of the add-on (0.1.3.1-signed). 

I may add ability like for built-in "New Tab" button: show button after last tab, if it's placed just after tabs:
https://github.com/Infocatcher/Private_Tab/issues/90

[Added later]
See new version: https://addons.mozilla.org/addon/private-tab/versions/0.1.4