I moved from Safari to Firefox a year ago (never used Chrome as my primary browser.) The reason I moved may sound really really dated, but I discovered that I can configure Firefox with separate search and URL fields. I //HATE// that UI and wanted my separate boxes back.

I wish I could find a extension that removes all motion on a page (video, js animated stuff) but I suspect that would be too difficult to do. I do use a extension that removes all color, but it doesn't work terribly well, and some UIs on websites are too dependant on color as differentiators.