Interesting idea. I don't generally need to download videos, but it is great feature. Good to know for people that like to download these videos.
For now isn't just better to have video embedded by linking directly to youtube and using hooktube just for downloading selected vids?
I mean we could possibly need to manage another interface (updating and so on)..
It will be interesting also to see how long they can live, because they are clearly "datamining" youtube, so google won't probably be happy with that ..