Rated 5 out of 5 stars

You say that this plugin only makes since if we can't use flash but I am using pentadactyl and need html5 video on youtube so I can use hints on the video controls and so flash won't steal keyboard focus.I can disable flash to make this plugin work but then all other sites that use flash won't work. Is there no way this plugin can just override flash on youtube?

EDIT: That is really great! In that case this plugin is flawless. Upgrading to five stars! Yay!

This review is for a previous version of the add-on (1.0.4.1-signed). 

I implemented this feature two days ago: https://github.com/klemens/ff-youtube-all-html5/issues/6
The new version will be released soon!

Edit: New version 2.0.0 released!