This all sounds really encouraging. I've become a vocal supporter of Firefox again since switching back a year ago. On that note, it may seem trivial to the average user, however it would be great if the powers that be could consider not forcing UI animation on the user without any possibility to disable it. IMHO one of Firefox's greatest assets is it's rich legacy in user choice and customization. Many users (myself included) reluctantly switched away for performance and security reasons back in the day. With that said and while sensitive people are a minority group, we do exist and UI animation can cause elevated stress and fatigue.