I like the concept and the customisability. What does not work well is pinned tabs. When Firefox is closed and reopened the pinned tab is gone.

Fantastic! Thanks!

Great extension for any multi-tasker, end of story.

This extension is absolutely essential for doing research, looking through programming references, and general reading and browsing. I don't remember what I used to do without it!

If you open lots of tabs, then TST is a must! No other browser or add-on can manage your tabs as easily or efficiently. This app is the reason I use Firefox over any other web browser ^_^

This extension is the USP of Firefox and the reason I still use this Browser! Thank you so much Piro (piro_or)...

I wanted to like the Opera group tabs extension is now absolutely useless!

Tree Style Tab is my first reason after security and privacy to use Firefox. I really can't imagine browsing without such an extension. Great job, Piro!

Great addon, but tabs got scrambled once in a while, which completely messes everything up. It's not happening very often, but when it happens, you need to spend a lot of time to fix it.

the best tree style tab extension I've tested so far!

Great extension! I love being able to organize my tabs in this way, have been using this for a few years now.

Minor complaint:
The recent update that recently (I think?) introduced keyboard shortcuts that interfere with nominal text editing, e.g. Ctrl + Shift + Left/Right, which I use for highlighting words.
The keyboard shortcut editor is generally buggy, as I can't figure out how to disable a key; trying to set it to something useless, like Ctrl + Shift + / or pressing ESC, doesn't work; I can only sometimes set it to "undefined".

May just jump directly to wherever the config lives and kill the keys.

EDIT: Hup, it's already filed and fixed - awesome!
https://github.com/piroor/treestyletab/issues/1995