I just upgraded my iPhone 4S from iOS 6 to iOS 8. Just before doing the upgrade, I had iTunes backup the 4S. I would think at that point, it would have transferred all purchased apps to the computer. So after I upgraded to iOS 8, I had iTunes backup the 4S again, and now it is "Transferring Purchases from iPhone 4S" - almost 100 apps. Not sure why it's doing that - it's not like I bought 100 apps right after upgrading. Makes me wonder if I'll end up having duplicate apps within iTunes. I was going to restore that backup on my new iPhone 5S - maybe I'll end up with duplicate apps on the 5S?