Gave it another try and it indeed working now. Before the download button would not appear. But now it appears and it downloads videos. Changing my review to reflect that it works now.

( 4 Star !!! if problem fix early i will give you 5 star !!!! )
Hello Team i am using this extension from more then 2 to 3 years , and very trusted Extension and never disspointed to me , but now this week if i am trying to downloded any video its correct but size is showing 0 Byte and it says currept or damaged ???
so please fix it as early as possible thanks you ♥ & Support from India

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.

Proche de la perfection en termes de facilité d'utilisation ! Toutefois ce serait bien d'être prévenu lorsque le téléchargement est terminé...

I have installed/uninstalled it about 6 times but it will not "show" itself on the toolbar with my other add-ons. Here are my issues:
1. IF you have lots of add-ons, this will cause a problem. The ICON here does not match the one that will appear on toolbar. Will be hard to "match", "find" on hi-resolution desktop. Here it is an "down" arrow pointing to a line" but on the toolbar it is not and too small for me to see it.
2. I don't remember the install sequence I used to make it finally install but it was not exactly like others add-ons but finally got it to install and works OK.
The issue of no AUDIO download is not an issue with me as there are lots of "strippers' and converters" as I EDIT my MP3 to remove crap from front and back.

Зачем расширение переводит русское название в транслит?!!