It works pretty well. Unfortunately, HD (720p) and more require server processing on the part of the addon's developpers (Youtube having split up sound and video), hence a paid license.
NOTE TO THE AUTHOR(s): a feature allowing to download both files anyways would be nice (without the requirement of server processing on your side): I have tools for merging and converting those files myself locally via an Open Source program.

Waste of time, requires paid account

works great and updates regularly...Peace

This is the easiest to use and the best video downloader out there !

Paying account. Why they not say thaat before adding it to browser?!

Have used it for years and it works like a champ. If it doesn't work, give it a day and it will again once the dev's circumvented G's new code.

"Free Service" but can't download MP3's without paying?

Developer always keeps it up to date.

Una de poquísimas extensiones que hace lo que se necesita, eso se agradece.

This add-on IS easy to use.
I just installed it and downloaded a video. Perfect.

Excellent and bug free way to download some special music vids that aren't available any other way. thanks!

The best ever. When youtube change codes and all downloaders stop working, they are always the first to work again.