Good Addon, Except Rated 3 out of 5 stars
Good addon except it causes the bar at the bottom left of the window, that gives the url of link that is hovered over, to be dark with no text or text the same color as the bar. Kubuntu 13.10, FF 28.0.
Rated 5 out of 5 stars
Great extension. Still waiting for the tab grouping function, though.
For those of you wanting to autohide vertical tabs try this extension https://addons.mozilla.org/en-US/firefox/addon/hide-tabbar/
it works great.