I installed this after upgrading to Firefox Quantum because Greasemonkey 4.0 is basically unusable right now :( I meant to try out Tampermonkey instead, but all that came up when I searched for it was Violentmonkey, which I had never heard of, but I was desperate to get my scripts working again.

I'm so glad I installed this! Not only does it work wonderfully with Firefox Quantum, but it works better than Greasemonkey EVER did, even before Quantum and 4.0. Scripts that I thought were broken now magically work! Odd quarks on certain pages that caused me to have to turn off GM to use those pages are no longer an issue!

It's a breeze to install scripts from around the web (it works with GitHub!) or from your desktop, and it's so wonderfully easy to just make a new script - the built in script editor is awesome.

Do yourself a favor - uninstall Greasemonkey, install Violentmonkey, profit :)