I ordered my upgrade to 4S (64GB white) at mid-morning yesterday, by phone with an AT&T rep. The email asking me to accept terms and conditions was stamped 6:20pm and I did that process within that next half hour or so.
Then the second email with the shipping order number was stamped 1245am today and I read that this morning around 8am.
That email invites me to check status by phone or on the website, and yet both methods still produced an error message for me when I tried. That was approximately 25 hours after my order was placed. I have stopped being concerned about it though. I will try later in the weekend.
Bottom line the upgrade is in process and has been in process since mid morning yesterday. They took my dough, they know (or knew) SOMETHING about my upgrade at a number of different data points per their mails and account notes, and the gist of the second email is correct in that they plan to ship just the phone and a sim, not messing with my rate plan in any way.
When I checked my account overview late last night (i have two lines), they had the status of my eligibility for upgrade on the primary line marked as "unable to determine" but there was also a note in the details that an upgrade was in process and that I had accepted terms and conditions. So I figure it's all about just a boatload of processing, a number of databases on tons of servers and they're wading through it all as best they can. Must be fun to work at a carrier or at Apple during one of these launch periods, ai ai ai.
