Pending
I just called AT&T and spent a long time on hold. They are definitely a bit bogged down by this right now. The lady I spoke with was very nice, and she admitted we probably all know more than they do at this point and they are just following Apple's directions. She said she had 43 other people waiting after she finished with me, so they must be having a fun Easter!
Anyway, the steps so far:
1) Once you call AT&T, they will ask you to provide your IMEI number which is on the Settings > General > About screen. If you try and do this now, you will probably have to wait on hold for a while.
2) Once you get through AT&T confirms things on their end--this only takes a minute or two once you get past the hold queue. Then, AT&T submits a request to Apple.
3) At this point you are pending with Apple. She said it may take a few hours before the move on it. That is where I am, as I just got off the phone.
4) Then, you are supposed to do a Backup & Restore in iTunes, and hopefully Apple commits the unlock at that point and you are good to go.
I am just going to wait until tomorrow before I even try as I am not really certain how to tell if it works. I'm not really in a rush anyway, but I am stoked that this is finally happening.
EDIT: Well, I couldn't wait, so I just backed up and started a restore. The phone is in the process of restoring now, and there was a message in iTunes that says "Congratulations, your iphone has been unlocked." So, if that is any indicator, it doesn't take that long once you initiate the process with AT&T. There was no code, or anything like I saw on some other sites. I just called AT&T and started the process. They sent the approval to Apple, and after a bit of time a backup & restore should confirm.