When I got the 6, I tried 3 different AT&T stores and none of them had the model I wanted. Couldn't try an Apple Store that day as the closest one was an hour away. Even at the carrier store opening, they didn't have some models. Why don't they prepare for these things?!
I can second this. AT&T ships FedEx overnight or two-day. Last three years I've had extended shipping dates but every Thursday morning before launch I wake up to a shipping conformation with FedEx overnight and have received my phone on launch day.