Let me get this out of the way: It's very well-designed. It does exactly what it says, and it does it in an intelligent way. It actually looks like an official dark mode on every site. The only problem is I can't use it effectively because it murders your CPU and nothing will load. And it's not like I'm on a Pentium 4 that can barely handle Firefox itself, I'm on a $200 hexa-core from 2 years ago running at 3.9 Ghz.

In short, it's well-done, but it's so poorly optimized it's virtually unusable. I would gladly go back to it if I could actually use it.