Just not on Windows with Firefox. There's still a major rendering bug that makes uMatrix mostly unusable. You can't get to the XHR or frame columns, meaning things like reCAPTCHA aren't usable unless you simply turn off uMatrix for that site.

The current workaround is to open the log and allow/disallow from there. But you can't get to the log button 99% of the time because of the rendering bug.

Not sure if it only affects the Dev Edition of Firefox or not. It certainly doesn't affect the Linux versions, neither Dev or mainline.

Really wish they would fix it. Here's how it looks on reddit, notice how much of it is unreachable: https://i.imgur.com/UHN7AQD.png

I'd love to help, I just don't have the time right now.