> The Mail app will now randomly play the "new mail" sound.

It’s not quite random: it plays the sounds as it gets new email, but then it takes anywhere between a couple of seconds to a minute for the new email to be visible in the UI. Infuriating.

> Xcode was stuck upgrading in the App Store. It would start the process and never make any progress. Cancelling it had no effect. Rebooting cancelled it but the second attempt, while making progress, ended up failing with a generic error message with no actual information.

I just normally kill the store-related daemons when that happens.