it's ok for some things but can be pretty flaky.

Often it requires the companion application... which is not such a big deal, but even then it can still be distinctly unreliable.

I have a Video Downloader app on my android phone which does a far better job, is much more dependable, saves in sensible formats, offers a better choice of download resolution options, in a much easier to follow way.
The android app also does simultaneous multi-downloads of the same files so you can download a big file in five minutes on the phone what take this addon twenty minutes to do.
By comparision if that android app got a 10/10 rating - which by my book, it does, this barely gets a 3/10.

I regularly have to just give up in disgust at this add-on's inability to save files and switch over to my phone.

Also I've downloaded files using this addon to discover they are in a ridiculous webm format - absolutely not useful to me at all, whereas the android app saves using the much more standard MP4 container.

The app developer really needs to take a long hard look at the alternatives and up their game if they wish for this addon to stay relevant.