This is perhaps the best add-on suited for my use case. I love arranging my tabs in a color coded way, and I like the container feature of firefox. This extension has enabled me to use the said feature effectively. It's not perfect, but the best for me.

That being said, I had some issues with the experimental features(of course). When I switched to enabling headers for all containers directly after never was selected, many duplicate header tabs were created for the same tab. However, It worked perfectly for only unused tabs. When I switched to having tab headers for all after that, I found only one duplicate of a no container tab. These are many of the expected problems apart from unexpected behavior sometimes.
Overall, I liked the add-on and would definitely recommend, but don't expect perfect stability.

This is the closest I've come to using an extension that provides what I liked about Panorama. I like being able to sort and create new categories in the sidebar but for whatever reason when I use this extension from time to time pages will no longer load. I'll see the loading animation on the tab but nothing appears. When I turn this extension off then the page loads normally. It's frustrating and it's the one problem I have with this extension. Even when I clear the browser cache and history then quit and reopen Firefox it still happens.

Suffers from same "bug" as "Simple Tab Groups". When closing private tabs with open windows deletes all tab upon opening firefox again.

This seems useful, particularly for Chrome migrants. It could use a better interface for hiding/showing groups, and it clashes with the simple groups addon, but I do prefer its functionality. That said, it's a very intrusive set of permissions, so I'd feel more comfortable if Mozilla got around to verifying it.