Google Checkout revenue had been "invisible" to retailers who use tracking pixel to monitor sales can conversion. As of last Friday, Google now offers a XML spec tell Checkout how to generate a tracking tag on their checkout confirmation page. Full details on Google Checkout blog last Friday. RKG pixel tag fully supported at the order level -- this new Google API doesn't share back SKU level info with the retailer or the agency.
Good work, Google Checkout Team --- thanks for providing this important transparency.