It sort of works, sometimes. Often times the video will start off at the preset speed, but about 30 seconds in, drop back to standard 1.0 speed. If you use the same tab to start another video (click on related etc.) it never works and will always play at the last speed youtube thinks it played at (1.0 unless you've manually adjusted it), so more often than not, this doesn't work. It's nice when it randomly chooses to though. Hopefully the developer fixes the bugs.