Very easy to use addon with some minor customization. I'd like to be able to whitelist/blacklist websites to auto-apply (or not) the filter to, instead of having to do it by visiting each site in turn (it also more often than not breaks the website's formatting if you enable/disable the addon, forcing you to refresh the page).
There's also some flickering between the light/dark themes I've noticed in Google Sheets specifically when you enter a tab, but it only happens a couple times. Does exactly what I need in there (darkening the background but leaving the document whatever color it should be) and works well so 4/5. Just a few bugs to iron out and some more QoL features for the options page.
EDIT: I've noticed that it lags some sites, especially noticeable when scrolling. Disabling the dark mode entirely resolves it. I may end up removing this addon as it's proving more annoying than helpful.