Thanks for the review Artemy, this is my first Firefox add-on. I did think about adding !important as I was putting this together, but decided against doing so initially, as I figured designers would only include such CSS if it's what they really wanted to see, and my first goal was to revert the new built-in rendering change. To date, I haven't seen any site that does so just yet, but I hardly go to every site on the web ;)

I plan on coming back to this to add the override as an option, and explore how add-on option screens are implemented and used. That said, if you have already seen sites where overriding the style would be helpful, I'll happily add the !important, let me know if so. I doubt anyone using this would object :)