I've used other youtube downloader extensions and this one does seem to earn its #1 rating. This one is self-contained (no other extensions or converter programs necessary) and works as advertised with some nitpicks. The download button does not show up when viewing videos in a playlist. It would also be nice to have an alternative to the download button in the menu bar (in case youtube does another sneaky interface update). The extension's built-in description in the add-on manager is a little messy and could be made to look more professional (as appropriate for such a useful extension). Although there are other downloaders that can work with sites other than youtube, I don't mind this one working well with just youtube.