Excellent job of darkening. But, as I use it more and more, I find more I would like improved. Now 3 stars, 20251107.
1. I can not (afaik) darken as subsite, e.g. www.ebay.com/itm. I can only darken the entire domain.
2. I can not add ANY entries to the SITE LIST. All I can do is change the few that are there.
3. new (20111107): I just discovered that Dark Reader is darkening not only the web site, but Firefox's control areas. (The tab bar, the location bar and the menu bar, all of which I display.) This is HORRIBLE. It makes some fields in these very difficult to see. Sadly, all these fields are not named GUI controls, which may be the reason. Particularly annoying since I spend much time customizing ALL the colors in those fields with custom .CSS.
4. The addon is very difficult to manage. There are essentially 2 ways.
A. Left click its icon on the location bar. This opens a Dark Reader control panel.
1) I can't scroll it and can't seeall of it. I use a 150% Windows magnification level. that's probably why.
2) I have no idea what the SEPIA value does
3) THIS CONTROL PANEL DOES NOT ALLOW ME TO CONTROL ALL THE SETTINGS I CAN CHANGE.
B. Right click its icon and choose "manage extension"
1) here we find controlling the shortcut keys
Why do not A and B include all the same stuff?
5. The documentation for this addon is only fair. (Otherwise, I would have learned all the above. I READ DOCUMENTATION for almost everything)
This include operation and use of the addon
and info about recent updates.
6. Functionality: The addon does a POOR job of handling shades of gray (actually all colors, but this is the most common example since many websites lack interesting use of color.) It says it darkens bright colors. But, it should also then brighten light color to retain contrast. Webpage areas in shades of shades are often turned unreadable.
7. Money
I would contribute, but find no way to do so. All I saw was a "buy it", but I don't even remember where I saw that.

the 3 rating is muchly due to the fact that some of these issues I have mentioned long, long ago.