In fact, the title says it all: Firefox (the official release) now supports 60FPS on YouTube without any tricks.
I noticed it the day before yesterday, as news about the Russian found - decided to make a note of ultrashort.
Update: commented
qw1 , due to the fact that YouTube has established HTML5 (but not Flash) as the default player for Firefox -
www.youtube.com/html5
Source:
geektimes.ru/post/251252/