It looks great and works as advertised. However it bogs Firefox down *very* quickly. After install I found tabs taking forever to load, links would hang after clicking them, and some pages would completely freeze in transition for almost a full minute. Closing firefox, shutting any process left in the control panel down, and reopening it will resolve the issue for about 5 minutes, and then everything hangs again. I've found a lot of dark mode extensions do similar things, but this one was the worst, and fastest, to do it. Uninstalling the extension resolved every issue I had, and if you're having similar issues you can see it's firefox by opening the task manager, selecting more details, and viewing the memory usage of the app before and after removing or installing the extension.