I think it's pretty good, but it's not stabilized for external clients. I'm not suggesting it's unreliable, but the API is not designed for third-party clients, meaning (potentially breaking) changes get implemented and deployed as the developers see fit. Actual SN employees would need to weigh in on the priority of doing this, but it would assuredly slow down feature development in SN itself if the API was intended to be used in a reliable way by third party clients.