A colossal improvement over the standard tab bar.

Frankly, it's long past time we collectively killed the standard tab bar for good. The standard tab bar disgusts me.

I wish someone would make this for Android Firefox.

E: 5 yrs later, this is still say half of the reason I use firefox instead of chrome

please import this extension for chrome or opera or vivaldi, i cant handle firefox anymore

This is my favorite extension since 2003.

A complete overhaul about tab controlling... It becomes one of the reasons that motivating me to keep using Firefox today (with no exaggeration :P

(Fixed, with extreme swiftness. More congratulations)
Piro, the savior of Firefox. Many, many thanks.
But I think version 3.5.7 broke TST Hoverswitch, equally fundamental for me.

One of the best things that happened to FireFox (IMO).
There are few quirks but I circumvented them by disabling cache, drag of tree tabs to another window and most important by shutting down TST sidebar before closing browser (that last part prevents from "mangling" order of tabs inside tree at launch).
Thanks to that I can safely manage 2000+ tabs on small Atom based CPU.

P.S. Please remember that one can hide FireFox native tab bar at top by editing profile file userChrome.css and adding lines:

/* to hide the native tabs */
#TabsToolbar {
visibility: collapse;
}

/* to hide the sidebar header */
#sidebar-header {
visibility: collapse;
}