Here’s some great news! If you are an iPad Wi-Fi + 3G owner on the AT&T network you are in luck.
You can remove the SIM card from your old iPad and insert it into the new one. Viola! You’ll have instant access to your current AT&T data plan, account, etc.
Apple representatives explained to me that all iPad 2′s are sold — unlocked. You can use any carrier compatible SIM card in the AT&T version of the iPad 2 (or actually any iPad).
So my AT&T 3G connection on my new iPad 2 was up and running instantly with my old iPad’s SIM card. I’ll end up giving the unused SIM card to the person buying my older iPad.