Nice Rated 4 out of 5 stars
Some of the pictured options are only available in older versions, probably due to new versions of Firefox breaking them. It would be nice to get them back sometime though.
It would be particularly nice if this extension were updated to use the latest FlowPlayer version, as it currently uses a very old version (1.21, while the latest is 2.22) and it's sort of buggy.
I still like this better than the default YouTube viewer, if only for the fact that it doesn't start videos playing on page load, meaning that I can load lots of videos in other tabs without having to go stop each one so they don't all play at once. That one feature alone is worth it.