As I understand it it's not a problem of the API but the nightmare of layers upon layers upon layers together with the promise that this will be hidden from you. (Not that having to fumble out what that REST service is actually sending back to you sounds that promising)

But the last three SOAP services I had to swallow ..err.. consume, leaked their abstraction over my desk and I had to start to xpath my way through responses from a Java service after having curl'ed my handwritten requests to the other side. This was not due to a problem with the published API but with the protocol annoyances as such. (e.g.: your OrderClass is not my order_class and your Array() is not my [] )