Works, Integral, Does Flash Too Rated 5 out of 5 stars
Flash and Video Download (which worked on more sites) stopped working. It had a button in the bottom add-on bar. The button ceased to appear.
This add-on adds a button under the video which is so integrated with the YouTube site that you'd think it were part of the site (indeed, it is so integrated you may miss the button).
It also gives the option to download flash (and not just mp4). You have the choice.