My understanding from a post in the forums (cannot remember who mentioned it) was that when the new web site launched, you would not be able to repurchase something that you have already bought. I selected a book that was listed in my account as already being purchased, found it on the products area and then started the purchasing process. I made it to step #3 which is the confirm payment method and address then canceled. The very next button to hit was the "Place Order" button.
Just wanted to throw that warning out there.
