It work and i recommend it.

Very fast because it's not using a 3rd party converter/download service but you directly pull the video from YT as fast as your internet connection allows you to.
The download button sometimes takes a hot second to appear, which would be a nice fix.

Gave it another try and it indeed working now. Before the download button would not appear. But now it appears and it downloads videos. Changing my review to reflect that it works now.

there is no download button under the video players.

So Far I have had good results with the extension. I'm able to download any video at 1280-720, mp4 or webm format. The speed was impressive at first but slowed down to moderately slow. I doubt the extension is at fault here and I suspect either my ISP (Comcast) or google not sure but I'm giving the author 5 stars.

update: 12.30.2019:

I added an extension called "Magic Actions" it sometimes allows the download button and sometimes not. Now it is showing a two download buttons.

It does what it's supposed to do.
Absolutely love it

640x360 px only