Initially I had some trouble with Firefox, but now it works great. I was disappointed that it didn't work on Waterfox—until I discovered that it DOES work, but the icon is not visible! When I first open the browser it pops up for an instant and then disappears. But if I click the blank space where it should appear, it works just fine. I've tried all the icon options and so far, none are visible but I am hoping a future update fixes the issue. In the meantime, it still functions perfectly. Great addon.

NOTE! The last update fixed it in Waterfox and now the icon appears in the toolbar. Developer response gets an A+.