Braintree — an online payments processor — aims to have a developer-friendly API for integration and touts excellent customer service as one of their strengths.
I have been on the phone with these guys several times this week as I integrate our subscriptions at GreenWizard
BT guys, if you’re reading this, feel free to use this as a happy customer testimonial. Keep up the good work. Your sandbox is also a pleasure to work with (unlike a major gateway who’s name rhymes with paypal).