I've used this add-on for a couple years and recently upgraded to Pro. It has worked reliably (and fast) for a long time and has been easy to use.

Recently, YouTube made some programming changes which broke the add-on, resulting in the "Download" button not appearing. I've been in touch with the author who says that a fix has been created and is in the approval process. It should be available in the next update which should auto-install.