The SharePoint Team have cleared up the confusion around Operating System support for SharePoint 2010 on their blog.
SharePoint 2010 will support only 64-bit (x64) (NOT Itanium) versions of Windows Server 2008 SP2 and Windows Server 2008 R2. SharePoint will not install at all on 32 bit Windows, or any earlier version of Windows such as Windows Server 2000 or Windows Server 2003.
SharePoint is not supported on ‘Server Core’ installations of Windows Server 2008 and R2. The Server Core installations of Windows server do not contain some of the components required for SharePoint to be configured or run. SharePoint is not supported on Web Server 2008, Storage Server 2008, HPC Server 2008 or the Foundation versions.