If you are a developer and you are wondering what the delta really is for developers, you are in luck. The Windows team has written such a document (Migrating your Windows 8 Consumer Preview app to Windows 8 Release Preview) and it goes into incredible detail for you.
This paper provides guidance and tips for migrating code assets built using the Windows 8 Consumer Preview released in February 2012 to the Windows 8 Release Preview. It includes porting guidance, a change manifest, and helpful details for developers who are tasked with migrating apps from the Windows 8 Consumer Preview. It assumes that the reader is familiar with the Windows 8 Consumer Preview.