They're good, but very risky. If you send it to a wrong email address, your money is gone. If the recipient deletes the email by mistake, the money is lost for ever. I wish we had the option to directly send it to an Amazon user with the help of their registered mobile no. or email address with Amazon. It should facilitate to check the recipient's name before confirming the transaction just like UPI. Paytm, Phonepe, Google Pay, etc. have this feature already.