Video DownloadHelper left me with little else to desire, it just does everything it's supposed to do - grab even difficult to capture video streams (which the website tries to make difficult to grab), copy the URL... It has succeeded where others have failed me.
I imagine it could be made even more user-friendly (although it is already), and some download manager integration would be nice as well (instead of having to rely on the Firefox built-in functionality. My downloads don't go through my default manager unfortunately. Maybe they'd be faster sometimes otherwise.