I'm using Braintree for my new app (https://www.getcloak.com/ https://www.getcloak.com/) and am extremely happy. They have incredibly responsive customer suppor

I'm using Braintree for my new app (https://www.getcloak.com/ https://www.getcloak.com/) and am extremely happy. They have incredibly responsive customer support, both business and technical. When I reported a unicode-related bug in their Python API, the technical team responded coherently within a few hours and released a new API revision within 48. Can't beat that... On the API front there are some minor issues. For example, their subscription API is excellent except when dealing with upgrades/downgrades. Upgrades can be prorated and billed immediately; downgrades (sensibly) must wait until the next billing cycle. Unfortunately, the downgrade is _recorded_ immediately -- you don't have a notion of a pending plan. Hence a user can downgrade/upgrade repeatedly during a _single_ billing cycle and end up spending an arbitrarily large amount of money.