IOS 5's "Cleaning" Behavior 
I write several offline mapping apps, and this is totally throwing us for a loop. We're recommending our power users not upgrade to iOS 5. Users download gigabytes of maps to their cache directory, they don't want to eat their iCloud allotment with that, or their slow their iTunes sync. But they also don't want to have to download those maps again, or find themselves in the middle of the woods without the maps they downloaded.