Works well. I needed a replacement for my old FireFox 56 Addon (BitTorrentWebUI) that stopped working with the new Firefox, and this one definitely does. Very happy with it. I like the fact that it adds a context menu, so that I can choose to download either locally (just by clicking on a Magnet Link, and it fires up in my local uTorrent), or I can right-click and send it to my seedbox. Very nice to have that choice without having to copy/paste links like I did with the BitTorrentWebUI.
Get a PayPal address Mika, I'll buy you a beer. :)