The add-on is perfect... well it was perfect till few month ago. Got update, and youtube videos does not play hd, max goes up to 720p. I though samthing wrong with firefox it self. Tried everything - compleatley unistalled and installed firefox, put removed and put add-on again. Nathing helped! I didnt even though about addon malfunctioning, i though my pc somthing wrong. I even reinstalled fresh windows, but the issue didnt go away... Till today! I have downloaded another HD add-on, deleted this one, and gues what? Its working! Youtube shows highest quality automaticaly without doing nathing! You need to sort this out, as you lose a lot of users! One of them is me! will use another now till that one brokes :D and may back to this one if it will be softer after few years or not!