What payment gateways do you use for your app?
dasil003: We use Braintree.  They have a secure vault similar to Authorize.net CIM for storing credit cards safely without PCI concerns.  Also, they were the only payment gateway that could give us true multi-currency support.  Apparently in most cases you need revenues at least in the 7-figures to swing that, but Braintree set up USD, EUR and GBP for us on the cheap.  Note that some payment gateways will claim to support multi-currency, even though what's really happening is they are just doing an exchange rate conversion and the customer gets nailed with an unexpected conversion fee from their bank.