Over the years, I have tried quite a few programs for downloading online videos. Most of them work sometimes but not always. So I kept trying until I found DownloadHelper more or less accidentally.
DownloadHelper has not let me down at all. It takes two clicks only to start a video download, the speed is limited only to my rather narrow local bandwidth which is a specific German problem. The download is faster than the actual display on screen and it even continues if you change websites.
Firefox displays an optical indicator of download progress or, alternatively, a detailed screen with pertinent data.
So far I am using DownloadHelper all the time.