Although MCP7A is a highly anticipated chipset with the best IGP performance, a number of manufacturers have told OCWorkbench that they're concentrating on the discrete chipset P43, P45 and G45 instead of the MCP7A.
They claimed that they were disappointed by the performance of MCP73 which features an IGP with a single channel DDR. Furthermore, ram compatibility is an issue with the earlier chipset. They don't seem to be confident that the MCP7A will get all these problems resolved in time.
There are also some manufacturers that have them ready for display at Computex Taipei 2008 though. Maybe we will see running demos of the new boards based on the MCP7A chipset.