It's a good tool to separate the browsing spaces, however, I find it somehow half-way between the private mode and the regular mode.
For example, I have opened multiple sites in several containers, then I have checked the cookies set by various sites by going to Options -> Privacy and Security -> Cookies and Site Data -> Manage Data. I was surprised to see them all, without any classification. The extension doesn't allow a per container management of the cookies.
I was also expecting it to let me choose which other extension is enabled in any of the containers, but I guess that feature might need an implementation at a lower level.
Later edit: I often start a regular tab because either I forget to long click on the "+" button to start a container tab or I press Ctrl + T (I am used to it). Maybe the Ctrl + T shortcut should open a new tab having the same type as the current one.