Rated 5 out of 5 stars
Works 99.999% ... unfortunately it broke the Youtube large player switch.
In fact, it breaks "the other button".
If you disable Flashblock, restart Firefox, then you can turn the large player on; now if you enable flashblock again, it's the small player that will not work (which I am kinda ok with).
Now, for the overall add-on, it's definitely a 5-stars.