I've read the other responses for the reasoning behind updating the UI the way it was... studies, interviewing, theory, etc. I'm sure that was the same thing Microsoft execs were pointing to after the awful reception of Windows 8 that caused people to ditch Windows because they didn't know how to get back to the UI they enjoy and are most productive with. I have been using FF since it was released, and I have never once thought "Wow, this update wants me to rollback or use a different browser", but that changed with this one. The first thing that stood out what I can't even read my inactive tabs. I don't like that it changed to my windows scheme. I know it can be changed, but still... I don't like the change to the nav buttons. I'm not fond of the firefox menu being moved and losing the bottom icons. The only reason I ever use Chrome is because sometimes Chrome just runs smoother and for a period of FF releases it would play Youtube videos choppy. I do not like the interface, but this is how I feel like FF is leaning towards. I know I can use the Classic Theme Restorer, but most people don't. Plus, it is totally inconvenient to need to get a add-on to do it. I think FF would be better served instead of making these kind of changes to the UI without a heads up you should at least inform the user that there is a new UI style available upon update and ask the user if they would like to switch to it and use it, and provide a way to change back if it doesn't suit their needs. You need to remember, so much of us do more than just surfing the web. I do all sort of development and I have my UI dialed in a very specific way that gives me the most productivity. So for FF to basically saying "We know what's best for you" or "After a few weeks of being annoyed you'll get used to it and come around" or the other stuff that is being insinuated to detractors of the new UI is not a good strategy for those that depend on their browser of choice for more than just entertainment and communication. Give people the choice and they will make the choice that is best for them... don't give them the choice they want and they'll go elsewhere. Again, I know the Classic Restorer is available but it never said that during update, never asked if I wanted to revert, so most will never make it that far. They'll just get frustrated and maybe they don't leave FF that day, but that experience will tarnish the way the user feels about the brand to some degree, small or large.