Rated 4 out of 5 stars

It was great while it lasted. With Firefox 57, I had a choice of downgrading to ESR/using these extension or moving to 57/58 and not using this extension. I moved to Firefox 58 and given the substantial improvement in FF 57/58, I am glad I did. Many thanks to the developer but it is time to move on to 57+

This review is for a previous version of the add-on (1.5.9). 

Use custom CSS code for Firefox 57+ ( https://github.com/Aris-t2/CustomCSSforFx/issues/2 ) to keep classic ui features.