Forget it. It used to be decent and now they ruin your video with an ad link to their program! Absurd. There are firefox add-ons that are not this intrusive and do not require $30.00US to remove. Look elsewhere.
Absolute cr@p! There's hardly any video from youtube on which it works without error, especially if I just want the original size file and not a version in which it has to use the converter and put the giant QR code on it.