Very useful for grabbing a copy of audio and video files from various websites. Works well most of the time or at least it used to, it has more difficulty now with videos that it shows as "DASH stream" and some other odd formats that seem to be getting more common. I think it is some kind of optimisation that breaks the file into pieces so they all have to be downloaded and reassembled which takes time and processing power. Maybe not the fault of this add-on though.

Always works much better in Firefox than in Chrome.