I was originally too "afraid" this was complex to use - not that it would stop me, but I thought it was something more than I wanted to spend time with browser.
Luckily I tried it, and very quickly realized that for me it served exactly the same purpose as NoScript - only easier. The use of scopes is fantastic - used te be that in NoScript if you allowed a domain, it was allowed on all sites; now you can select to allow things on particular domain only with the Custom option, but it's still not as flexible. And on µMatrix I by default allow on active scope, current domain - only things I know I'll want on whatever site wants to use it I'll allow for *. In NoScript you could certainly learn such habit, but it's more cumbersome, so you only go for custom rules for domains you specifically are allowing as exception on the site you're on. And even then it's less flexible than µMatrix scopes.

The only negative thing I have to say is: no version for Fennec. That is the mobile versions of Firefox, android in my case. On android FireFox I'm still stuck using NoScript.
I would likely hate using this UI in Android Firefox, but that's because of how Mozilla designed their current add-on UI system and is no better with NoScript - so come on, write that android version. Maybe try inventing slightly different UI that better fits the portrait mode while at it ;)

And thanks. This is golden.