It would be great add only if it will be more stable ... Very often groups are missing or tabs are not in their groups after (re)start of browser :-( Sometimes helps to switch panel into another view and then again to Tree Tabs, but many times I lost the tree structure definitely. Several times all tabs were lost (after firefox update) and addon started a crashed again and again.

Great bu buggy...
the tabs all appear in the same group (loss of structure).
Plus various bugs monthn annoying.
And sometimes all the tabs disappear. This morning, I lost everything, it's not acceptable: I give up to find something more reliable.

Sometimes there is a bug where all the tabs are extinguished.

Дерево с вкладками разлетается... почти всегда(((

1. sometimes add-on is loosing the sorting of tabs and all tabs appears in "ungrupped" tab
2. two time add-on losed open tabs at all
3. almost always add-on restores the closed tab in the wrong place where the tab was closed. Mostly the tab is restored at the beginning of the next group
4. there is a problems with a focusing on tabs when current tab was closed

so.. it's raw

unfortunately i just lost all ~100 tabs when installing "context seach" addon last (after tree tabs), keeps crashing. all tabs gone. i dont know why.

this addon would be perfect for me if it would not constantly crash the whole system...firefox remains to be unstable
also for wide displays the option to eliminate tabs on top view?

I've switch off automatic tree structure. Nevertheless, sometimes it closes many tabs when I close only one — like they was affilated. It's terrible.

Been using Tree Style Tabs for years but found this and decided to give it a whirl. After three days, decided to clean up a mess of tabs. Selected one tab to keep, clicked "Close other tabs," and sure enough ALL other tabs closed. Unfortunately that included ALL my pinned tabs!! MAJOR oversight!!! Uninstalled. I'll stick with Tree Style Tabs. I find it far better designed and better thought out.

Edit for added detail: A few other reasons I've ditched this in favor of TST:

Messed up the order of pinned tabs
Doesn't have a decent way to organized tab groups automatically with good settings
Appearance settings are way to convoluted. Users shouldn't have to be web designers to understand what to do with appearance settings. There ought to be a few graphical examples of choices. Keep it simple stupid. Simplicity is always better.
Honestly, I find the appearance in terms of usability far to cluttered.

In short, IMHO, Tree Style Tabs is so far ahead of this extension in terms of feel, look and usability right out of the box this one just isn't worth the time. Yet...

.

Tabs ungrouped and got loose everywhere, when Firefox restart.
I guess it'll never work if it does not have Session Manager intergrated.
I thought I found better replacement for Tree Style Tabs, but no, just the same.

Organizing tabs in a sidebar? Amazing! Easy to use, friendly use, everything is fast, lacks some functions, I have other addons for that.

But why does it reverse the order of my tabs? I open Tree Tabs, it creates a pretty tree, top tab is my last right tab, everything is ok.
But after I move my tabs, the top tab in Tree Tabs is suddenly the most left tab in my browser? I move multiple tabs at once and suddenly the order is reversed? What?

Since it makes it terrible to use in mass organizing of 50+ tabs (I use 500 tabs in one of my windows) and I cant find "reverse your tab order" addon here, this makes the addon completely unusable. This addon is simply beaten by others because they work, this one doesn't.

Requires access to ALL data from websites. Why?!

You have the sidebar and the tab bar so what's the point. Beside you can not hide the siebar whenever you want it get stuck there. It is annoying.

what is the point of this if it doesnt hide the tabs at top? they appeared again after I hit "detach tab", on all my windows. also, not a very ergonomic interface, little to no control over size of tabs.... I will not use this. good effort I guess?

Duplicates tabs on horizontal + vertical. Can't have bookmarks open at the same time. Trees are not apparent enough.
But since it's the only one working for now with the new FF versions that's all we have

Doesn't remove the native tabs toolbar like any proper vertical tab extension should, rearranging tabs won't affect native tabs toolbar, and flickers when switching tabs.

It's more of an issue with Mozilla than this add-on, but supporting their decision to remove all existing add-on functionality and use this instead is stupid.

It does not work for me and there is no change after working on addon settings, on FF 53.0.3. But I am looking forward for updates.