Even v4 was too much for me. I liked the UI pre-v4, and for the longest time after v4 released I would use the FF2 theme (back when themes meant more than just putting an image on your chrome - but that's a whole post by itself) and various extensions (Classic Theme Restorer, Status-4-Evar, and a few self-made Stylish userstyles) to preserve the look of pre-v4 as much as possible. It was comfortable for me.