UI Geekery
I'd like to explore an esoteric point about how you label the buttons in a dialog box. iTunes 4.8 just made a great improvement in the confirmation dialog that greets you when you try to delete a track from the database.

Here's the dialog in 4.7:



And here's the same dialog in 4.8:



See the difference? Apart from the much-improved wording of the alert, the labels on the buttons changed from "Cancel", "No" and "Yes" to "Cancel", "Keep Files" and "Move to Trash". This is more important than most developers will credit. When the buttons give you a Yes/No choice, you absolutely have to understand exactly what the dialog is asking you. If you have verbs on the buttons, you're a significant proportion of the way to knowing which you want just by the verbs and the context in which you're presented with them.

In an application (or on a platform) which extensively uses Yes/No/Cancel, the user can become conditioned to choosing Yes or No depending on which is the most-selected option. If a common dialog says "Would you like me to make a nice backup of your file so you'll never lose it?", well you would always say Yes, right? What if one in a hundred of these dialogs says "Would you like me to cryptographically shred your home directory? Yes/No/Cancel" - the strong possibility is that the user will again choose Yes, but this time with a disastrous outcome.

Even worse are dialogs which present a negated question and require a yes/no answer: "Would you like to proceed without saving your document?" Yes? No? Well, let's say Yes, because I always say Yes to questions about saving.......

I'm glad that iTunes has improved this dialog because I have made dozens of errors with it.