I like the add on and it's simple to use.
Idiot proof, I'd say.
When video is ready to be downloaded it simply starts to glow the icon. And once you click icon it'll pop up a list of formats to choose from.
Only minor thing I'm missing is ability to define my favorite resolution, so for example I'd like to get 720p link as first possible option and 1080 as second. Or have fixed order always, but add-on is trying to remember my previous choices, but sometimes it mix the order of the formats/resolutions so if you are downloading few videos in a row then first choice in the list is not always what you prefer, so caution and reading the offers in details is needed.
Also page title is displayed in download options pop up, which is helpful, but it seems to be in fixed and quite big font and if page has longer title, then it's not going to fit.
In general I like the add on, using it time to time, and I thank those who made it, because it's true helper.