I bought an ipad because of the unlimited data plan. The I learned about this madness from att. If you see on this page here
http://store.apple.com/us/browse/home/shop_ipad/family/ipad?mco=OTY2ODA0NQ
scroll down there is a graph on the right hand side showing data plans. Unless this changes soon you will see under the unlimited section a fine print thats says
"* Available if ordering iPad from the Apple Online Store by June 6"
It does not say anything about activating before, says order by. I called att and they said its up to apple, apple says its up to att...***? Finally got in touch with this guy who said that att will honor this and so will apple...who knows.