One thing which I’ve long wanted to do with my ipod was to easily keep it filled with a random selection of albums. Not songs. I don’t like listening to songs at random, likewise my squeezebox is most often used in “random mix album” mode (the only caveat being with albums fitting on two CDs – there’s an option to tell it to collapse multi-CDs albums in a single one, but while you want this for a concert spread on two CDs, it’s less useful on a boxed-set of 10).
So I wanted to have the same thing for my ipod, and the solution is simply a playlist which randomly selects albums. It’s actually very easy though not quite obvious.
As a digression, I was also looking for a way to automatically expire old mail in some folders under Mail.app. Again, no specific feature for this, but it’s very easily done with filtering rules. The common point in this is that a UI is kept simple by making some of its features powerful enough that they can serve other purposes, rather than adding more features which would be rarely used. It’s a hard balance to strike, though.