This may come as a surprise to some of you, but debugging applications on the iPhone is no picnic. I know, crazy, isn't it! It's next to impossible to get the information you need from a customer's device without building in some method to send the user's preferences, data, etc. right into your application, which just seems messy.
Luckily another developer has created the iPhone / iPod Touch Backup Extractor, which extracts all of the data for an application from the backups made by iTunes when you sync your device.
What a wonderful thing. Thank you, Pádraig.