Rated 5 out of 5 stars

I somehow missed the "Private" checkbox in the menu when right-clicking on an open tab, and the dotted underline is a sufficient indicator; It's just that it isn't easy to see against certain colors. You should probably change it to a more prominent color.

This review is for a previous version of the add-on (0.2.1.2). 

Rated 4 out of 5 stars

But I have a couple of problems with it. I can't use the right-click menu in the tabs area, because it conflicts with TabMixPlus (I know this problem isn't easy to resolve) & it needs an indicator of some sort (as other reveiws have said). I did notice the dotted underline on the private tabs, but it's barely visible in most cases.

This review is for a previous version of the add-on (0.2.1.2).