That's what I'm using. And I like its capability. But as I said, the first-time process for getting a site isolated (if you tend to isolate sites often) is cumbersome and I feel there could be a shortcut button for [create new container -> assign site to new container].
Ah, I see; I tend to isolate all sites I trust in the same container and everything else goes in a temporary container so I mostly have one trusted container (along with one for each of Facebook, LinkedIn and Google).
To add a new site to a new container, I manually edit the file (accessed through the pencil button) and add the line with the proper syntax:
!*.sketchy-website.tld , My Isolation Container
It allows me to define that I want that for all subdomains in the same workflow. But I have to admit it is far from easy for someone who is not already used to this.