Video Download Helper stays in the race against Youtube.
For a while it was getting blocked from downloads, but it caught up again. Kudos, especially since so many others are no longer in the fight.
Some of us simply have connections not suitable for live HD viewing, so it is neat to be able to download a vid for later consumption without buffering :)
Sometimes, you need to reload the page, or run it in a private window, but that is Youtube mucking around.
I also have the Ghostery add-on, and that seems to even help as well :)