Unusable in latest version of Firefox, unless you are happy with default extension options. They are unchangeable. Support request yielded response of "support is for customers only" when I informed them of the bug, even though the extension page lists that email as a support option. Oh well. Off to something else.

Useless because it's ONLY for smartphones, not real computers that businesses use.

Overlay does not work on Nightly
UPDATE: overlay still doesn't work on Nightly AND you can't edit the addon's options in Nightly.

I use buffer on a regular basis for our nonprofit NGO to post contents from our webpage to Twitter and Facebook.
Works fast, reliable and rock solid. The only drawback I found so far is that on Facebook, the author always is "buffer" and not me. But maybe I just haven't found the right button yet ...

In 24 hours I have gained at least 50 followers.

One of the best extensions I use

Heads up I was stuck on 3.3.x even though I had auto-updates on. Had to manually update to 3.4.2 which installed as a separate extension rather than replacing the old one.
Overlay still opens in a new tab, but at least I am current.
As others have said the Chrome extension is much more polished/feature rich, and it would be great to see the FF extension get the attention it deserves, particularly with `Quantum` released and now v60.

A great way to publish material to social media.