The charges are about the same as your merchant services account. No other monthly fees or expenses.
We have used it for two years with only one issue, or question from a customer on the tracking number of a product. It may have come through a CSR and the communication system in Seller Central. We provided the tracking number and it was no issue.
No A-Z claims, I don’t think they apply. Though we run our website with similar policies to Amazon. Over 50% of our sales pay with Amazon Pay. We offer Credit Cards, Checks and PayPal in addition to Amazon Pay.
Only complaint, we use Wordpress and Woocommerce, they present Amazon Pay front and center. Not on par with other payment options. And yes, we have tried to alter the code to “fix” that.