I was up at 7 this morning trying to reserve my phone, but could not get past the AT&T portion of the Apple site where they look up your AT&T account information for renewal and service plan information. I spoke to The Guy, and the way to get around that is to reserve a phone at least at an Apple Store via their new iPhone Apple Store app. I did that, now will have to go through the activation and service plan information in the store. I'm sure it'll be a mess then too.
Edit 5:21pm: I chatted with The Guy about 3:40 and he was just finally able to order his phone on the AT&T website. Basically it says they are not guaranteeing delivery on the 24th. I tried about a half a dozen times since I got home and I was finally able to put a phone in my cart and order. It took 2-3 rounds to pay for it, but managed. I have a confirmation number. I've yet to get a confirmation email. My luck is the phone will arrive after the 25th. We shall see.