Before I was using Unseen (https://addons.mozilla.org/en-US/firefox/addon/unseen-fb) but this add-on hasn't got a button like FB Unseen. Good job!
By the way, the popup menu has got a bug, the label of all 5 options points to the first one. If you want to check/uncheck some of the other options you'll need to press the check square, its label won't work.
EDIT: after using the version 2.0 for a few days I had to remove it because Facebook messages stop coming when the add-on was enabled. On Firefox 48 on Windows 10 when using the Facebook small chat windows I could send messages but I couldn't receive them having to do a page refresh to see them. What kind of huge bug is this? I've downgraded the rate from four to two starts. I'll carry on using the old Unseen until new releases of this extension.