After 2.5 hours of failed attempts on Apple and AT&T since 3am, I went to sleep and woke up again at 8am. At that time, I was able to get through to AT&T**, ordered, and got a confirmation email.
** Ticked though because
1) I didn't need to wake up at 3am in that case.
2) AT&T's website activated the Pre-Order button for the iPhone 4S, but after entering your info, it led to a page of only iPhone 4 options. This wasn't the case for everyone. It was for me and some others. I know it was their error because at 8am, I went through the same steps and ah, there it was, the iPhone 4S plus iPhone 4 options. So somebody forgot to flip the switch, and I hope that error on their part doesn't result in my order being delayed.