I have escalated tickets with both Magento and UPS right now, but I don't seem to be getting very far very fast. I'm hoping one of you has run into a similar problem and can point me in the right direction.
UPS XML is configured exactly to spec: full production everything, all fields are correct. I've had both UPS and Magento review and troubleshoot my configuration. According them, it looks fine. Tests run by UPS have confirmed that my rates are functional and should be reflected in XML API.
No matter what I do, no matter how many hours I spend trying every single combination of settings, I cannot get negotiated rates to work on my Magento Go store. My shipping rates display as equal to or greater than retail prices with an error level of $5+ per package.