Super flexible, a must-have.

Awesome!

After a year or so of not using this extension, I was very pleasantly surprised when I installed it again today. It seems a lot more stable than what I was used to.
As a Tree Style Tab user, I highly recommend this extension.

Edit: The latest update has a much clearer layout which can be opened in a separate tab. Very useful.

Thanks for pointing out the Firefox bug that prevents add-ons from running by incorrectly flagging them. I love the Tab Session Manager. I rock 4 windows with ~20 tabs on each at any given time. Thanks a mill!

What I wrote previously (ignore):
"Please get your add-on signed, it has been removed from Firefox's list of approved add-ons and thereby inactivated on my computer. I'd give 5 stars otherwise."

From now Firefox works only with signed add-ons.
Please sign your add-on.

PS temporary solution from Firefox docs
about:config xpinstall.signatures.required = false

The best currently for Quantum.