I noticed that since the introduction of iCal, the calendar function on the iPod was going remarkably slowly. Too slow to be useful, actually (how useful it now may be to have a calendar in your MP3 player may be disputed, but that's another discussion...).
When I was fixing my regular G4 drive I thought, why not run Drive 10 on the iPod. Said and done. The iPod showed up as it should, and it optimized and defragmented the iPod. And to my surprise, the ipod now is as smooth as silk when changing categories, even with the calendar functions.
[Editor's note: I do not have an iPod (nor Drive10) to test this hint with, but as always, I'm more than willing to do so if someone sends me one :-).]
Mac OS X Hints
http://hints.macworld.com/article.php?story=2002101405222825