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.