It appears (from the AAL at least) that 'Amazon Payments' is still listed as an immediate/integrated payment option for US sellers in the 'Successful BuyNow (selling) Confirmation'? This is taken from the AAL of #33522447 for example:
The invoice will include buttons for immediate payment via PPPay.com, PayPal, Amazon Payments and Google Checkout (if you selected any of these in your payment options).