To all you guys telling us to use the Apple Store App: You do know that all that is doing is possibly reserving a phone on a first-come-first-serve basis, and that it's not even checking AT&T for any of your essential information like discount eligibility or data plans?
In other words, you're going to have to wait in a line as long or longer than the one for walk-in orders and have a very good chance of not getting your phone on launch day. Of course, even if you do get in before the cutoff, you're depending on the same sh*tty AT&T servers that failed today, likely under another massive strain, with the added problem that none of your information has been ported over.
If you realize this, more power to you. If not, just know that you will be mocked mercilessly when you come here bitch and moan about it, and deserve every bit of that scorn.