I tried a lot of video downloaders in the past few years. This finally is the one I am most satisfied with:
* apparently finds every YT video
* easy to use
* minimal permissions needed
* in case you have a question about the addon you get an answer within very short time :-)

And I am with el gusano who wrote:
"This add on does just what it says. For all the whiners out there, read the directions. Make a donation, you can load the higher quality videos; the 360 is free just as advertised. If this keeps up with upgrades, I will donate more later just because it's a good product."