I don't see any Microsoft Retail version out yet and the OEM Builders version mandates you don't buy it for yourself.
Something odd is going on with the new Microsoft licensing so I've subscribed to hear how you dealt with this.
I am using Bootcamp on my mid 2012 MacBook Air (OS X 10.8.2 - Mountain Lion) to run Windows. I am currently running the Release Preview of Windows 8, but I am looking to upgrade to a full version. Is it possible to upgrade from Release Preview given that I did not have a previous version of Windows installed before the preview (clean install via USB)? I've had some mixed answers from googling. Can someone say if they have upgraded to W8 Pro from Release/Consumer Preview without a previous version of Windows?