I've worked with plenty of APIs (> 50). The biggest headaches I came across are bureaucratic stuffs rather than poor API designs. For example, there are vendors (like ConstantContact) that requires you to provide your credit card to get an account for API testing. You know what, they auto-bill your card after X number of days and require you to call them up to cancel your subscription. Because I'm on the other side of the world, I've to drop them a call in the middle of the night just to cancel billing.
If you ever find yourself in that situation again: send them an email and explain you’ll contact your bank and issue a chargeback if they don’t cancel it without a phone call. The issue very quickly resolves itself; chargebacks are expensive.
The power is in your hands; use it. Don’t play their games.
