Hi Jim,
I have that same question as to when Amazon Pay will be integrated into StoneEdge or if there is an add-on to allow it.
We have been using Amazon Pay now for over a year now, and have been very pleased with the results. It's not as big as our PayPal payments, but it's starting to get closer and we get a lot of comments from customers that are happy that we offer it as a payment method.
You can import an order that is Amazon Pay, but until the import module has been updated with this payment method it won't show up as Amazon Pay and you won't have the transaction number. We're on Miva and were able to get a copy of the StoneEdge import module from a Miva developer and we were able to modify it to allow StoneEdge to import the payment method and transaction number, but we have yet to figure out how to show it as "Paid" (like when we import PayPal), so we have to manually mark each of the AmazonPay orders as "Paid". If anyone knows how to mark them as paid on import, please chime in.
Other than that, Amazon Pay's interface is easy to use. We have to log into Amazon Pay in order to issue refunds and handle disputes, but other than that it's pretty simple, and Amazon handles the fraud aspect of Amazon Pay, so that's another reason to use it.
Hope that helps.
Cale