I picked up my reserved phone at the Apple Store at San Diego Fashion Valley. They were doing their part to minimize the impact on ATT, LOL.
They were activating in-store using iTunes, and the in-store and activation process itself was very pleasant. Once you got to the front of the line, a sales associate would meet you at the door and walk you back to a waiting area, asked what phone you wanted, went and got it, took your credit card, came back again (lots of exercise for the employees!), then walked you over to the activation area and did the activation.
I was told (apparently erroneously) that activation would take "up to an hour", but that some people's phones were activated "as soon as they walk out of the store and get a good signal".
I walked around the mall for a bit, but no dice. I returned to the store and asked. I was reassured that it would eventually activate.
Several hours later, no activation.
Read some posts here, decided to do a full reboot, and it instantly activated.
Would have saved a lot of people a lot of grief if they had just rebooted customer's phones, and/or suggested a re-re-boot if it didn't work. They were apparently telling everyone to just walk away and it would take care of itself. They were consistent about this, as the guy at the door told me the same thing when I came back to complain.