As others have said, there is an issue with the video having no sound. I chose the 1080p version of a file, and the resulting file has no audio track at all.

But I do appreciate that I can download the subtitle tracks, that is useful. (It comes up in the list of video formats After you click the format you want in the little popup icon)

Personally between this having no video, and VideoDownloadHelper putting a big watermark, your best bet may be to use both and then combine the video from the former and the audio from the latter :/

it does work, but around the time i installed it my browser started working really hard, even past the download
not sure what's up, but i'd only run this in a virtual machine from now on