I like to run all apps maximized. That way, I can focus on the task at hand and not be distracted by stuff going on in other apps. Also, less clutter = more productivity.
I work on a website and I use two 24" monitors. Firefox maximized on one (Firebug takes up tons of room you know!), and screen (with emacs/terminals/etc) on the other.
I think this is more a personal preference thing than anything else. (And I use my laptop for music and IM, but its usually displaying the Vista enter password screen anyway.)