This extension simply cannot fail to work in half of the pages, it's either works or doesn't work. Half of the pages means it's not being used properly. Most frequently conflicting software has been installed. Same as if it works 100% for one person how possibly it will work only in half of the cases for another person? My conclusion it's a defective user. It's about thousand people using this extension and less than five people experienced difficulties. I guess be proud.

You mean you modified your Firefox config and expected this extension to work? You are the first one of 441 people with working extension, who had done something so dumb and then gave negative review. This extension only works on unmodified Firefox once you altered config it will not work. It does not work on cats, bicycles or pizza either, is it the fault of the cats or the human who was trying to do that?