Gamedaily.com has a reply from Microsoft about the new heatsink found inside the Xbox 360 GPU:
"Microsoft was deliberately vague in its response to GameDaily BIZ. The company did not deny the inclusion of new heat sinks, but it wasn't exactly confirmed either."
A Microsoft spokesperson provided them with the following statement:
"Regularly updating console components is commonplace within the industry and is a standard aspect of the business for a variety of reasons including cost reduction, improved manufacturability and improved performance. We do not provide details on these updates."