Multi-Account Containers makes my life with multiple clients and many identities much easier. Great add-on if you have more "contexts" in your online life and you want to keep them separated.

I have multiple clients for my business with many overlapping web services which I need to log into with multiple accounts simultaneously. This add-on is perfect for my needs and solves a real problem for me.

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...

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).

An extremely powerful extension that allows you to have multiple accounts for the same service on Firefox. It's a great tool for separating your personal and professional life without having to use more than one browser. It's easy to set up, simple to use, and your containers sync across your Firefox account.