An awesome addon that makes it easy to isolate work tabs and personal tabs containers allowing you to login into the same site with a different Identity in each container. The ability to give default containers for a site is also super useful.
Areas that require improvement:
Make it easy to edit list of domains to default container associations

Сама идея приложения хороша, но однажды вылетел браузер и приложение после запуска забыло все пароли и настройки, какую вкладку в каком контейнере открывать, а сегодня я отключил все плагины в Firefox, включая Мультиконтейнер, (нужно было проверить работу браузера без них), а после включения увидел, что Мультиконтейнер плагин забыл все мои вкладки (а их было настроено около 20-30), настроенные с таким трудом и временем, и показывает те 4 вкладки по умолчанию, которые были сразу после его установки. Синхронизация постоянно включена, но не помогла.

Great Add-on!!
Nice to tidy up and organize Tabs. I like the possibility to easily separate websites, which shouldn't get in touch.

Just needs some additional configuration-tools +sync!
-rearranging containers, inclusive default (as I need it), is a must have! (I need default Tabs at the end)
-Pages in a container+settings(like always open in container X) have to be synced to other firefox-devices!!
-also to android
-more symbols colors
(- Advanced Options)
These point are not given at the time I reviewed it!

..would be nearly perfect, improves my experience a lot!
I really want to give it 5 Stars!!!

Very useful. I like the new features (always open, hide container, etc.)

Very nice, still missing some features – that would make the Containers a solid alternative to multiple Firefox profiles/Chrome's „people/supervised users“. Especially that Firefox forces a single instance (I consider this a deep architectural bug by itself).
1. Synchronization via Firefox sync.
2. Setting a default container for a domain is clumsy arnd unclear.
3. A better integration with Password Manager (..., History, Bookmarks, Addon Manager, Preferences,...) would be very nice.
4. A possibility to reopen the current URL in a different container is a must!
5. I'd expect that container tabs inherit from the „default“. Currently, the „default“ is just an ordinary container without any added value, just a bit different menu/toolbars/uncolored tabs, which is misleading.
6. Protect containers with a password? Especially if the Password Manager would be containerized.

Also it is not clear, which Addon is „THE containers“. There are many extensions on AMO with very similar functionality.

Очень удобное расширение. Как разработчик, часто приходится тестировать сайты, и контейнеры позволяют не запутаться между тестовым/продакшн сервером, а также помогают хранить раздельные аккаунты на разных сервисах одновременно. Короче, очень удобно)

Houd verschillende zaken makkelijk gescheiden binnen dezelfde browser sessie. Werkt heel goed en makkelijk.
Keep different stuff separated within the same browser session. It works like a charm.

Missing points:
- Configurable container icons (not only more, but the possibility to add our own icons)
- More colors (or visual patterns! like dashed, dotted...) options
- Default container: it should be possible to open (by default) all the new tabs into a default container if no specific match-by-domain is possible.
- External apps integration: It should be more easy to open links from other applications (like Slack, or Thunderbird) into specific containers
- Navigation History integration: It should exist a way to navigate through the navigation history filtering by container
- Temporary containers, something like this: https://addons.mozilla.org/es/firefox/addon/temporary-containers/?src=hp-dl-promo

Great
no need profile switcher again

Really useful!

Great extension but should provide more configuration options. I.e. open always in default containers. URL patterns, etc.

It's perfect. It would be also great to be able to collapse and expand a container.

Una delle migliori estensioni che potessi trovare: posso aprire decine e decine di sessioni separate senza uscire dal browser. Ormai non posso più farne a meno

Es muy buena para mantener las cookies separadas. Tener varias cuentas al mismo tiempo. Mantener la privacidad un poco contralada y las I.A. más productivas. Además de organizar las tareas por colorcitos jaja