My Firefox interface was exactly how I wanted it: simple, dark, and unobtrusive. Then an update apparently changed the default theme into a distracting purple/red color scheme without me choosing it. I had to dig through settings, themes, and add-ons just to get my browser back to plain black.
New themes are fine. New customization options are fine. Forcing a visual redesign onto an existing user is not customization. Give people the option to try it instead of changing something they've already configured.
A browser is a tool. I should not have to troubleshoot its appearance after an update because somebody decided my toolbar needed a personality.
