I use this add-on mainly to reduce tracking by Google search. I.e. when I use Google search, I don't want to be auto-logged into my Google account or associated with my activity in Gmail etc. My laptop has 3GB of memory, it generally cannot handle more than one container running at a time. Instead of opening every google service in a container, I just have a container for Google Search and another one for Amazon (I'm not a big facebook user, but if I need to log in there I do so in a different browser.)

This arrangement surely makes my browsing less private than it could be as I'm logged into gmail etc w/o a container; I also have to ctrl-click links opened from google search and gmail, otherwise they open within the container.

I rated the extension 4 stars because I would appreciate an option to open outbound links (like google search results) outside of the container, without having to ctrl-click each time. I kind of wonder why containers aren't built into FF? But with the extension installed, the functionality feels baked in.