This add-on is a godsend for me. So far it works perfectly and it also doesn't seem to slow down Firefox.
I watch and listen to a lot of things on Youtube and I hate the way it tries to shove all that garbage down your throat: users' comments, often inappropriate or offensive, irrelevant recommendations or even relevant recommendations that steal your focus.
I don't mind too much having ads on useful content if it helps supporting the ones that produced it, but all that effort to keep you hooked and consume your concentration is intolerable and I believe it's even more heinous than on old regular TV: talk about progress.
I'll be using this add-on as long as it is maintained. Thanks a lot to the developers.