I've only used it one day so far, but it's the best across-the-Internet darkener I've found. I plan to try it out for a few more days, and if it continues being this good, I plan to donate.

The only problems I've found is that an initial page load can be slower than it otherwise would, up to two or three seconds perhaps, and the menu for the extension itself can be slow as well, but it doesn't happen on repeat opens, and I think it's worth it.