Is great with few bugs that if fixed would make it a 5 star.
Bugs:
Tabs merge with other panels sometimes
Shortcuts don't work when sidebar is not displayed
One of my panels lost all tabs once
Moving group to new window causes tabs to fall out of group
Extra Features:
Make snapshots more usable allowing you to rename them, remove and add tabs, organize them, restore or take snapshot of a selection, etc.

This is the only thing keeping me on firefox.

Their is simply no other browser that has tab management that comes anywhere close to firefox + sidebery.

The extension might be buggy from time to time when you have a lot of tabs and run the nightly FF version (I have around 3k), so turn on the snapshot feature to avoid loosing tabs :)

Perfect work! Practical functions, modern design, and abundant customization options leave me with nothing to fault.

I have no words for it. I have tried all other similar extensions, but no other offers the same tools and fast experience as this one. It's perfect and the best one for Firefox.
There is only one function missing, which is essential, being able to pause and play videos that are playing, there is only way to mute, but not pause.