I know some of you have been asking about Windows 8 support for Civil 3D and the rest of the Infrastructure products. Just released is the current list of support Autodesk products on the new Windows 8 platform. At this time none of the Infrastructure products (Map 3D, Civil 3D, Infrastructure Modeler, etc.) are included in this list. The only one that is supported from the Infrastructure Design Suite at this time is 3DS Max Design.
Please follow this link to the technical solution for more information: http://usa.autodesk.com/getdoc/id=TS19048377
This technical solution will be updated as new Windows 8 compatibility information becomes available.