Okay, after three days, I registered because I got my phone working, and I wanted to try to help you guys as much as you all have helped me. Having all your various stories really helped me sort out what's going on here and now I've got a working phone.
Here's what's going on for people who have active sim cards, but iphones that still need itunes activation.
Your sim card is active, but itunes doesn't care, because it's not supposed to lag like things did on Friday, and I personally don't think they tested that situation before release. So what's going on is as far as AT&T is concerned, you're open and ready to go, but itunes itself has no way of handling this. What you need to do, is go to an AT&T/Cingular store, and have your entire account ported to a new sim card WITHOUT THE iPHONE DATA PLAN. DO NOT LET THEM ADD THE DATA PLAN WHEN THEY PORT YOUR ACCOUNT TO A NEW SIM. YOU WILL ADD THIS IN ITUNES.
Okay, now that I'm done yelling, we can continue. Once you have a new sim card in your phone, go through the itunes set up process just as you did on Friday night (only I didn't take the expanded text package, as I'd heard people say it caused problems. I will just add it this week instead). Select your data plan, accept the terms, and at the end it will activate your phone (there was no email, it just activates right there, in about thirty seconds, THEN it emails you.)
After that, toss your old sim card in the garbage, configure your email, and rock the **** out.
I know this wont help everyone, but my wife and I were both existing AT&T wireless customers (I came from cingular, she came from AT&T Blue), and this worked for us. Hope it helps.