perfect

Very good. The only one more feature I need is ability to set home page for container. I use some containers only for e-mail accounts or other one specific site and I'd like to have open this site automatically when I open container.

Really good. Really help me to check my accounts as if I wasn't logged in. Also it can help me to separate work and daily life browsing.

Great add-on, I use it for personal/work separation, banking, shopping vs. social media separation.
Works great, allow sync between devices, remember site>tab assignment

For IT - great when working with multiple identities in same services like o365

It would be ideal to be able to clean private data from containers. I love the option to clear browser data when closing it, but it would be very useful to be able to clean the containers in a particular way (or if there was one that was automatically cleaned when closing Firefox).

The only major thing that could be better, is having the tabs group together like in chrome.

Excellent for keeping accounts separate and from sites tracking you across the web. 2 small caveats: reordering containers doesn't seem to work under the "+" dropdown menu, and syncing to another FF instance doesn't migrate your custom containers. Not looking forward to setting up the additional 27 containers I use in each instance - and I use many...

Everything fine with this new feature like Multi-Account Containers but I can just add that I if you can do something with the history by container can help to no loose the different webpages that I visited, because the container just safe the current page where was my last visit, it doesn't show me the movements forward and behid that I made.

Hiding Containers don't work anymore

a bit finicky to set up

I use it primarily to have multiple Microsoft and Google accounts running in the same browser window. When used properly, it can also be a great privacy tool (to keep sites from knowing about each other).