Rated 5 out of 5 stars

UPDATE: The latest version 0.14.2013082301 has been released. I confirmed this newest version worked. Thank you for the prompt fix.
Same as akurei, this addons is the only reason I still use Firefox as Chrome dropped vertical tab option.
For some reason, the latest version 0.14.2013082201 did not work with Firefox 23.01 and WinXP, Win8 on my machine. I do not know other combination as I do not have the machine.To fix this, I just overwrote previous version 0.14.2013052901.You may have to adjust width of side tree tab.You can overwrite previous version 0.14.2013052901 from the address below directly.https://addons.mozilla.org/firefox/downloads/file/210628/tree_style_tab-0.14.2013052901-fx.xpi?src=version-historyHope this will be fixed quickly.

This review is for a previous version of the add-on (0.14.2013082201.1-signed).