This add-on is good only if the video you want is already cached. If it's not, then the download is extremely slow and unreliable.

If you want to download a video which is not already cached, and you want it in 720p or 1080p quality (or you want the audio in MP3 format), then you have to pay for the Pro version, which I did.

I paid $30 for the Pro version. However, it is only after you pay that you find out the software doesn't run on your computer; it runs on the developer's server, which is extremely slow and unreliable.

The add-on's home page states "Direct video download links from Youtube servers for maximum speeds coupled with instant high-quality (192kbps) MP3 audio downloads at blaxing fast speeds without leaving the Youtube website", which is an outright lie.

To download a file that is not already cached, the add-on instructs the developer's server to download ("fetch") and transcode the video, and then (if the stars are perfectly aligned) you'll be allowed to download the file from the developer's server.

As I'm writing this review, I'm attempting to download a video with a length of 1 hour 51 minutes. It took 33 minutes for the developer's server to "fetch" the audio stream and the 1.8 GB video stream, then it took 3 minutes to transcode the streams into a file, and the add-on has been sitting at "Conversion completed, loading file..." for the past 31 minutes. If this is like my past attempts with other videos, it will sit here forever and I'll have to close and re-open Firefox, clear the browser cache, and then try again (and hope it works that time).

I sent a support request and asked if there were any way to get this add-on to download and transcode the videos on my computer instead of on the developer's server, and the developer responded very quickly, saying it isn't possible. The download and transcoding process MUST occur on the developer's server.

I should also note that when I tried to download one video, the add-on said the video was geo-restricted, so it couldn't download it. I could watch the video without any problems, but because the download occurs on the developer's server, I couldn't download it.