This USPS module uses the Class ID instead of the service name as a key. This means that the module will keep working when USPS changes the class names. No more frantic changes to fix the module every six months.
This is DEVELOPMENT software. It should only be used on a test/development site. Early versions will probably not even return quotes. This addon will be replaced when the module is realy for a live store.
The development forum thread is http://forums.oscommerce.com/topic/393974-development-usps-shipping-module/