After some effort tweaking, I've finally set up Firefox's UI exactly the way I want it. Tiny bar at the top with the only commands I care about, menu bar hidden, all bookmarks quickly accessible from a menu ("Favs"), and tabs at the bottom. No wasted space. It doesn't look as nice as IE, but it's faster to use.
(Extensions used: Tab Mix Plus, Hide Menubar. "Favs" is the only entry in my Bookmarks Toolbar, which I've moved to the main toolbar.)