Unreliable and only partiallyl implemented. Transactions may fail - but Google only tells you that it isn't quite sure if the transaction has failed or not. They do not even pass along an error message or reason code or anything. They leave you to figure it out on your own. There is not even a record of the attempted transaction. So - people are submitting millions of dollars of transactions through what they might think is a banking app, and key elements of tracking these transactions are nothing more than vaporware. This is software? Not yet.