I'm using it for couple days only, but I like it much more than Tree Style Tab. Love the "Panels".
Finally tab-organizing addon I might be happy with.

The best tab management extension for Firefox among all I've tried thus far (and I've tried a lot of them)! Very flexible, highly customizable and good looking. Very well designed!

The best side tabs ever. It has also container URL rules and User Agent URL rules for containers. Works much faster than any other side tab extension I have ever tried.

The best vertical-tree-style-tab extension (and I have tried a few before). A lot of great options and features, e.g. automatically moving a new tab to a defined panel based on the url pattern. It sometimes crashes after Firefox restarts, but the feature of periodic auto-saving snapshots provides a rescue. Thanks!

This is the best addon I've ever experienced on Firefox. Way superior to Treestyle tabs or OneTab for organizing my tabs. This addon is loaded with excellent features like proxy, useragent and container support.
Thanks to panels and tab saving you can organize and backup your sessions with snapshots without any hassle.

This addon is the only reason why I didn't ditch Firefox for Brave yet.

I've used Tree hierarchy add-ons since forever. Came from Tree Tabs most recently, but the sessions didn't work correctly, decided to look for alternatives. This add-on is amazing. The holy grail of Tree Tabs add-ons.

Top 3 stuff I enjoy:
- Groups and containers.
- Working snapshots (e.g. sessions loading)
- Highly customizable

The most features-full, esthetic, and practical sidebar.
Only downside is sometime minor bugs with tabs (disappears or wrong container), but reloading the add-on fixes it. Also the add-on is maintained and updates are frequents.

I can't switch to Chrome if I wanted: there is no Sidebery!! This works amazing. Firefox Containers gets you ready and Sidebery finishes it of. I used to have over 40 tabs. Now I still have over 40 tabs, but I grouped them into Work, Personal and Learning. Each showing only a dozen or so, bringing back my sanity :-)

Its beautiful. It works really really well.
The most underrated extension in the category of sidebars.The possibilities are endless. I keep discovering new features everyday.

Tabs on the side; Containers; Bookmarks; So feature rich! I've removed the default tab bar and used this add-on to replace it completely.

The BEST tab manager, I always loved TST but it was lacking some features which I needed like tab grouping. I discovered this recently and it is extremely customizable even suspends tabs automatically. The perfect tab manager I've been looking for. Thanks for the developer for creating this extension. Will never leave Firefox because of extensions like TST and Sideberry alone.

I came back to firefox because of TST and Sidebery made sure I'll stick with firefox. It does everything I missed in TST and looks beautiful. Animations where kind of laggy for me but you can turn them off in settings, so problem solved. Awesome extension, love it <3