Ive been happy with this addon I wasn't as interested in youtbe or other popular sites that a lot of these have been written specifically for.
I was looking to download source videos for a course Im working through since my internet connection is horrible at the best times.

Ive been able to get every video Ive tried for so far. a little inconvenient having to leave the browser open but I understand that some of these work by actually manipulating the data as the video is streamed in so need this limitation.

A little bit more info on available videos and maybe a little better UI would bump this up to 5 star easily enough I believe.