The addon is great, it has really helped me with my eye strain issues due to the increasingly popular design trend of low contrast and tiny text sizes. I don't have poor eyesight, but I like having a reasonable text size and contrast so I can actually read it without having to keep on re-reading it due to the uncertainty caused by it being hard to see.

There's only one major issue for me: When a neutral grey text is overlayed on top of a dark or black background, the addon only shifts the text to a darker colour like black - making it invisible! It would be good if the addon was aware of the parent element's background colour and to factor that in so that the text colour would shift more towards white rather than black when on a black background.