Pros:
1) doesn't ask for a lot of permissions
2) actually recognizes videos
3) actually downloads videos, and gives the user the option of where to save them
4) decent download speeds
5) download button in a logical place
6) allows downloads as MP4 or WEBM

Cons:
1) does not tell you the file size of the video you are trying to download
2) does not tell you the resolution of the video you are trying to download in some cases. Some videos will only say the file format and "Normal", which can apparently be any resolution under 720p.
3) Does not recognize all available resolutions. Very annoying to watch something in 720p or 1080p only to find out that it can only be downloaded in 360p.

Overall this is a very solid add-on imo. i've been looking for hours for a decent youtube downloader and this is one of the few that both works and doesn't stripmine my computer for data. Cons 1 and 2 should be easy fixes.

Con 3 is something most/all of the video downloaders are experiencing right now, so i have to assume it's more of a general problem with firefox or youtube rather than something specific to the add-on. Still hoping it gets fixed soon.

Many thanks to the devs for making a decent product, and i look forward to the next version.

update: 2 years later and this is STILL the best video downloader available. thanks again for making a good product.