Rated 4 out of 5 stars

With Tabs on Top, the mouse responsive area is bellow the menu/navigation/bookmark bar, not bellow the tabbar (similar behavior than Autohide Tabbar, but that shows a narrow bar to define the mouse responsive area in the original tabbar position bellow). With Tabbar on Top, and this extensions the tabbar don't overlay other tool bars bellow like Hide Menubar do.
But Hide Tabbar does not work correctly if used with VertTabbar, the mouse pointer responsive area to show the vertical tabbar, is placed horizontally in the previous position of the tabbar, though some people may consider this a benefit, specially if OS vertical taskbars are used (opposedly Autohide Tabbar responsive area goes vertical with VertTabbar); and with VertTabbar, the tabbar refuse to autohide unless key combination is used, or until you move the mouse pointer to the status bar, which may help if you want to toggle with the mouse, but provided that there's a hide after setting it's no crucial; curiously this flaw has no effect if you're in fullscreen mode.Also, a setting to config the number of pixels that define de responsive area for the mouse pointer would be useful.

This review is for a previous version of the add-on (0.7.3).