The most obtrusive recent UI change was the new tab switcher that tries to mimic the OS app alt-tab overlay bar. It was taking 30 seconds (not an exaggeration!

The most obtrusive recent UI change was the new tab switcher that tries to mimic the OS app alt-tab overlay bar. It was taking 30 seconds (not an exaggeration!) to load the first time I hit ctrl-tab on my fast desktop, and would randomly pause up to 5 seconds after that. It also turned what was a rapid-fire muscle memory action with an ergonomic behavior, into a slow and unpredictable chore. To top it off, it would always display full-screen, outside of my never-maximized browser window. Just glad it could be disabled. If you work on Firefox, or are new to development -- this is not Luddism, and don't let this attitude discourage you. Let it be a lesson that you need to understand your users and not just assume that everybody uses a maximized window on a 13-inch laptop screen with all day to wait for slow code to load.