I'll keep it brief for now as I'm on with Apple support, they're telling me this is an "emerging issue." I'm attempting to back up locally to my rMBP via iTunes and getting an error about not enough disk space. I have 100s of GB free so that's incorrect. Just a heads up in case others are having this problem. I'll edit this post with more details and any fix as I get through this call. This could get frustrating for anyone moving to iPhone 7 (like me) today and not using iCloud backup. First edit: the error message I get from iTunes is "iTunes could not back up the iPhone "Name" because there is not enough free space on this computer to save the backup." I'm on iOS 10.0.1 and iTunes 12.5.1 on latest El Capitan. edit 2: Mac specialist calling this a "pretty consistent problem with the new updates" edit 3: headed for tier two support... edit 4: Tier two wanted to reinstall the system files on my rMBP. Servers are under big load today (go figure) and it wasn't happening so I've just backed up to another Mac and settled that way for today. I'll reconnect with support next week to sort out the problem on this system.