well it's good in general but far from ideal. For corporate sites it's a must-have: its filter mode is often better than the corporate "Dark" mode even if it exists.


I miss a method to disable or alter modes based on the full URL instead of domain (this will immensely help for plaintext in particular).
Also it doesn't invert PDFs.

Three things annoy me about it: the slowness of the dynamic modes, failure of Filter mode to display plaintext files readably (they show them as an black text on an almost-black background), and inability to crate full-page screenshots with Filter modes (the part of the page which isn't displayed at the time of the screenshot doesn't have the inverted colours). This all annoys me far less than the white-background sites, like addons.mozilla.org (and there are others too which somehow avoid being inverted while not being protected).

The custom filter rules I set up are not synced between my Firefox instances (configured for the same Firefox Sync account), and are lost on every addon update ;-( So you better copy them somewhere and be ready to re-instate occasionally.