A $100 credit would have been even better but AT&T wants to thanks its customers (Hmmm...I wonder f it has anything to do with Verizon getting the iPhone also) by offering no strings attached 1000 roll over minutes. Apparently this should would work not just on iPhone but other phones also.
Just text the word "Yes" to 11113020 and you should receive a reply like above within a few minutes. Let us know your experience.
