I am working on it at the moment, but it is extremely hard. You have to communicate with them (through email) and describe what you want to do. They have too many requirements (like you should have the icons of MasterCard and Visa on your website) and it is even harder to convince them to allow you accept payments from the whole world (they usually only let you accept payments within your country).

With PayPal, everything is automatic. You can configure everything yourself and accept payments in no time, without having to communicate with an actual person from PayPal.