Rated 3 out of 5 stars

This used to be great, after the last couple of updates, it is not so great. It blocks some page elements and does not load them into the dashboard to allow them individually. But even allowing the entire website does not allow those elements to load, essentially breaking the website! They are still blocked until you disable the entire add-on or uninstall it. This behavior seems to happen mostly with embedded content (not exclusive to those though) that are not necessarily hosted on the current site. For instance, if I follow the link of a blocked embedded video to the actual video off-site (if possible, this is not always the case) then the elements of the video (CDNs mostly) will load in the uMatrix dashboard and I can allow them. After doing that, the embedded video on the previous page starts working...but not always.
This issue is relatively new, I only stated seeing it late December, early February, so hopefully it will get fixed.
Until then, the extra time I have to take fucking with it makes it not worth the effort. When it is fixed, I will adjust the rating back to five stars.
Edit in response to dev response: no it's definently something with uMatrix. i tested it in a portable install of FF with only uMatrix and no other extensions. A lot of the embedded videos that are blocked consistently are through Name That P***. Their webmaster has not responded to my emails. I will submit a detailed report at https://github.com/gorhill/uMatrix/issues, I am not comfortable posting links with any adult content here.
Thought: disabling uMatrix does not fix the issue, I actually have to uninstall it....maybe this is resulting from some sort of anti-adblock technology being employed by NTP? I have encountered a lot of popups and redirects there in the past.
Response to dev repsonse: Unactionable??? It straight up does not work on that site in FF. Please note that this DOES work in Chrome however. Perhaps the problem lies in a compatibility issue with FF itself.

This review is for a previous version of the add-on (1.3.2). 

> It blocks some page elements and does not load them into the dashboard to allow them individually

Nothing changed in uMatrix to explain the described behavior. Note that some extensions may prevent uMatrix from working as intended, for instance this is the case if you have NoScript installed and it is set to block 1st-party scripts -- in that case because of the way NoScript works, it prevents other extensions from seeing all the attempted network requests for scripts -- and thus in such case uMatrix will not be able to see/report these.

In any case, your review is unactionable, it lacks specifics to be able to provide a meaningful answer to the issue you are reporting.