Works pretty well for downloading private facebook videos/audio, which is what I use it for. Would be nice if it had an option to only download the audio instead of video.
My concern is the permissions it needs. Access all data for all websites? WHY? Why not just the domains from which you can download the content (that are listed in the description). It seems shady. I'd be careful around it. I recommend using a primary (master) password if you have logins saved in your browser, just in case.