TLDR: Find another solution to fill your download desires. Very disappointed with Mozilla for permitting this app to be marketed this way. Have come to expect better from Mozilla, though that is meant in the very best of ways since I've never encountered an app worthy of a negative review on the site before.

How things have changed. Seem to remember this working as advertised back in the beginning.
Now, not so much. Free add-on places an intrusive code in top corner. Can't miss it. To get rid of it or download in any useful file format or other feature you might need, you have shell out $27! for a "companion app".

Still spotty at best. But if you're into frustrating download experiences that end without you getting your download, this is definitely the app for you.
Strong pass.

Although it should be noted, most seem satisfied.