I really like the add-on, it does exactly what it says it does, and does it very well. It gives sufficient controls to configure, and selectively customise or disable the add-on on specific websites.

That said, I disabled it today after trying it for almost 4 months. Sometimes it slows down webpages too much, specially long pages (e.g. Github's webhook payload docs page), pages with visualisations (plots and figures, e.g. the coronavirus monitoring page by worldometers), and sometimes login pages.

I also have a hunch it's causing the memory footprint of my FF instance to bloat. I have a really beefy laptop (>13 gigs of RAM available), and it still starts paging after half a day. I do have a lot of tabs open, but I didn't have this issue before. If I continue to have my RAM issues after disabling the add-on, I'll come back and remove this paragraph.

Edit: now I have been running with the add-on disabled for half a day, with the same set of tabs, and my memory footprint is about 1/3-1/4 as before. Really sad that I can't use this add-on, back to being blinded on the Interwebs :(