We used the release of the new aluminum body iMac's from Apple as an excuse to finally get rid of our previous generation 24" iMac. We secretly (eventually not so secretly) hated it all along and I'm so glad to be getting the new smaller 20" iMac.
To be clear, we really liked everything about the 24" with the exception of it having a 24" screen. Staring at a 24" screen at close range is like sitting at the front row in a movie theater; you have to crane/rotate your head to see the various parts of the screen that you want to pay attention to.
I should disclose that we have the 24" iMac sitting on a narrow depth desk (24" deep) which means our heads are closer to the screen that most home setups.
I can't wait until our new 20" arrives.
As a side-note, I would have loved to have bought my new machine from the cool Apple Store at 20th Street in Boulder (keep'in it local), but they only sell standard configurations at Apple stores, and I always need to make some kind of hardware configuration change (usually more memory) on the machines I buy; annoying.