I don't know how important this is, but in 10.2 when you bring up the force quit dialog box, if an application is not responding, it is listed in red. I guess this helps to tell the difference between an app that is just processing, and one that is actually hung.
[Editor's note: Be slightly cautious using this visual guidance as the decision to force-quit an app. I've had the Finder show up in red when it was trying to access an iBook I had put to sleep (whoops!); it returned to its normal color after I opened the lid on the iBook. Still, it's a nice visual indication that the app you think is hung up is truly hung up.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020913062421870