I will give it one start because the second and the third most important features are still not implemented.

The second one is sorting. When you have many-many containers, let's say 100, it becomes nightmare to maintain order within them, especially when moving to a new PC.

The third thing that is lack is the ability to add domain masks (like *.google.com) instead of all sub-domains one-by-one to a container's list.

It would also be nice to have the setting to open all links not presented in the current container not in the context of this container. For example, when I open a link in a Google, I don't wish this link to be opened in a "Google's" container, it should be no-container tab.

It seems like Mozilla just released the product and completely abandon it right after release, without any plans to add new features, which is very sad. :(