In my limited testing it looks like I can finally watch 4K videos again! My system can handle 4K video, but apparently not 60 fps. Funny thing is in a chromium based browser there is no stutter, and I heard a rumor that if you change the user agent in firefox to chromium it would remove the stutter. You can specify sites to use a different user agent in firefox, you don't have to do it globally.

Is it just me or did google remove the youtube html5 player test as shown in the screenshot?

Nice Add-ons

The seems to have solved the constant freezing I had with youtube vids and with Firefox default vid codecs disabled.

Great doing its job

It's working :D, now I can play videos in 720 and 1080!