I've used CheddarGetter (http://cheddargetter.com http://cheddargetter.com) for a few projects and I've been extremely happy with their service. * API is reas

I've used CheddarGetter (http://cheddargetter.com http://cheddargetter.com) for a few projects and I've been extremely happy with their service. * API is reasonably nice to work with (wrote a Python client called Sharpy https://github.com/saaspire/sharpy https://github.com/saaspire/sharpy) * Lots of options to control exactly how and when your customers get billed. * Support for a bunch of payment gateways * Tools for handling tracked items and one-off charges (e.g. discounts or fees) as part of your subscriptions. * Fantastic support - I don't think I've ever waited more than a few hours for a response and their support team has been very helpful.