Rated 3 out of 5 stars

VEVO on youtube is fighting back on this and as of now this plugin in working great on all but VEVO videos on youtube. (it used to work)

This review is for a previous version of the add-on (1.9.5.1-signed). 

The newest version (1.11) should work with VEVO too, but I'm not sure for how long. You can get it from the website ( netvideohunter.com ) because here on the addons page the new version is waiting for the review from Mozilla before it's available for download.