I (like many others) was very disappointed in the performance of Word v.X on my G3/600 iBook. Looking through the various settings today, I stumbled accross something very interesting. There is an option under the 'General' section of the Preferences entitled "Enable Quartz text smoothing". This option is selected by default, and since I like my fonts nice and antialiased, I didn't think much of it.
I believe now however, that this option enables some sort of MS specific antialiasing, because if you turn it off, the fonts are still antialiased (though they look different ... better, but different), and everthing in the app speeds up about two times! The strange thing is that if I turn off antialised text in the system preferences (using TinkerTool), there is almost no speed improvement.
I'm not sure if this is an oversight on MS's part, or myself not realizing what's really going on, but it's made my Word v.X easily as responsive as 2001 under OS9.
Hope that helps some folks.
[Editor's note: I was amazed at the notable speed difference that resulted when the Quartz smoothing box was disabled. Even on a my G4/733, pages now scroll by at a much faster rate, and the text is still nicely smoothed. This same option exists in Excel (but not PowerPoint), so you may wish to disable it there, too! I don't believe that Quartz Text Smoothing is a MS specific option; I believe it's an OS X system option, but I don't know much more about it than that ... anyone?]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020802093020568