I've been using the built-in Containers in the Nightly browser since they first became available. Admittedly they are a power-user feature or for those that are vigilant about privacy/tracking.
I recently switched to this extension (over just the builtin version) to get the "Always open in container" feature which is pretty much indispensable due to external apps firing browser links (slack, email).
I wish there was regex/pattern matching support and literally any interface at all to see existing settings. The CookieAutoDelete extension has a great UI for managing cookie regex settings per individual containers - please implement something similar for this extension!

very nice add-on. i managed to log-in multiple accounts and never had to repeat logging in again but i hope we can password protect it so that other users of the computer wont hack the accounts in it.

Feature request: allow for Firefox Sync so multi-account container settings can be synced across multiple computers.

I would love to be able to tell this addon to open specific URL:s in specific containers, not just based on the domain name. My use case is handling several different twitter accounts, and based on which account URL I type it would be great to have it open in a pre-determined container.

It lets me do what I want with my multiple accounts without dealing with chrome or much hassle from my part.
I would love it if right clicking new tab opened up options for it or similar, keybindings would also be nice, it currently takes too long to click and hold, and is a little bit awkward.

I really like this addon, it's a nice intermediate to what I really want: concurrently running sandboxed accounts. Lately, however, it appears to be a bit broken. When I open a link from an email in Google Inbox ("Fun" container), that should end up in a new container (e.g. "Finance"), the new tab closes immediately, and I'm forced to right click to open the new link. This stinks.

I love the concept! It's private, easy to use, and should be BUILT IN to Firefox! I just wish you could add more icons, each container has it's own individual history, passwords, etc. Also, when I sort the tabs, it moves the new tab button to the left, and I can't change it back, which is annoying. What would be nice is if I didn't have to open a new tab in a container by having to go to the container menu. If it would be right next to the new tab button, where everyone would see it would be awesome. Overall, great!

Useful for keeping cookies separate. Would be nice to keep add-on's and their data separate too. For example, MetaMask should only be enabled in its own container.

Slightly disappointed. I hoped for different privacy settings for containers (like cookies policy at least). Now it just deletes all my cookies through all containers after closing my browser.
And would be nice to have the different addons set for each container.
I still need few browsers to solve this.

Awesome! 5-stars if I could easily take an existing tab and swap/copy/move/duplicate it into a different container (right now I have to copy URL, open new tab with different container, paste and go ... blech). Other people have asked, adding my vote!

Just add sync and open a new uncontained tab as a container and it will be close to perfection!

Would be nice to be able to move tabs over to a specific container and also be able to edit the list of domains in a container.

I absolutely love containers! They help immensely with web development and having multiple test accounts. No more private windows and using both Chrome and Firefox just to test more than 2 accounts at a time!

This add-on is useful for memory management and organizing the endless collection of tabs I seem to keep open.

I look forward to how the developers can make these easier to use and organize. Certain aspects about the implementation feel clunky to me, but the need is real.

5.0.1: the only lacking feature I can think of is one to move a group of opened tabs to a new window

Would be even more useful if settings (which site to open in which container) would be synced across the devices

Works great. Some irritations - no shortcut to open new tab in specific container. Can't specify the existing web site I'm on to go to a specific container - I have to open the tab container and then reopen the site in that container. Maybe I'm missing something? Would be 5 stars if I could do the above.

It's a great way to keep cookies from different 'worlds' (i.e. work, personal, etc.) apart. Just works, and I've never had issues.

That said, not 5 stars for a few reasons:

1. URL autocomplete is shared between containers
2. Login (username) autocomplete appears to be shared between containers

Good for increasing Privacy/Anonymity online by compartmentalizing tabs into their own little virtual sandbox of sorts.