I use Maxthon primarily, a wrapper around IE's core. As firefox progresses, I'll eventually switch over completely, I have it installed and use it from time to time. There are still some features I like in Maxthon that either aren't implemented in firefox or that probably could be if I looked into making extensions and whatnot, such as dragging URLs or text and it opening a new tab, and double-click a tab to close.
http://www.firefoxie.net/ has some stuff that can make it look "better" (assuming you like the Office XP / 2k3 style of menus, etc). I recommend skipping the step about "remove unnecessary padding" since it can make the menu's "jump" and just use the stuff for Office XP style menus, and the ChromEdit extension.