Ask HN: Any experience with domain name registrar API's?

I have to develop a Register Domain functionality in our project. I'm looking for an API service that does the domain registration.

It seems that Godaddy's prices (on their API Reseller program) are far better than others.

I started using their service and I'm still in development phase. But their API, documentation and toolset seem unmaintained.

Does anyone have experience with them? Are they reliable? Are there better choices out there?