I'd been using Firefox as my media browser; I can't reasonably set Safari to show on all desktops, or risk it crashing from stupid movies & music, so I need a secondary browser.
Mozilla's constant disruptive updates are annoying, but they just added a new "trick" to Firefox:
Yes, they've added ads & spyware, and enabled it by default. If they're willing to do this kind of shit, the next one won't have a checkbox, it'll just secretly sell everything you do to ad companies.
So fuck this, Mozilla is dead to me. The one thing I ask first and most importantly from any app or service is DO NOT SPY ON ME.
I've uninstalled Firefox, gone to Chromium for now, we'll see if there's a better option later.