I tried activating on my own this morning. It arrived shortly before 10 AM. After about 3 hours of waiting I just said the hell with it and went to the AT&T store. They were able to activate it for me. I'd imagine the swarms of people trying to activate their phones at the same time might have contributed to my difficulties.
What was truly funny, though, is that when I was being assisted at the AT&T store, my information never got loaded into the computer from their queueing system, so the lady was looking at the information for some guy named David. I don't know how she managed to not notice that I was, in fact, not David, especially after I handed her my ID. Needless to say, I ordered from Apple so apparently the activation process was doomed from the start. She ended up giving me a new SIM card. But since she had the wrong phone number and was thus working with the wrong account info, she ended up totally wiping out poor David's SIM card. I'd imagine he'll probably be making a trip to the store sooner rather than later.