10:32AM ET: Indeed, depending on what employee you talk to, in-store activation via iTunes is either "slow" or "down" -- but either way, they're handing you the phone unactivated, which needs to be completed by connecting to iTunes from the comfort of your home. Beware: if you're upgrading, your old SIM will be immediately bricked, so you'll be phoneless until you complete the activation!
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One of our own members, who happens to work for AT&T just sen tus this info:
I work for AT&T. The reason iTunes is running slow is due to the amount of users accessing at once. Apple is suppose to be working on fixing the issue. I know this because my POS system from AT&T is displaying this as a global message.