KUDOS TO APPLE
As noted below, my hard disk crashed last week. I took my computer to the Apple store on Wednesday, and they had it back to me Friday, with a new hard disk and 90% of the important data backed up. I had to spend a lot of time reinstalling software and reorganizing things, and I had to find a shareware utility to dig some "invisible files" off my backup drive, but all in all it was a fairly painless experience.
One piece of advice to Apple buyers: Always get the AppleCare. You're buying expensive hardware from a company that's best at software. Your computer almost certainly will need service. AppleCare covers advice from the store's Genius Bar and it also covers most repairs. (I did have to pay $54 for the data backup.)