mmoy, further down in your link MS says Opterons beat Xeons 10-30%:
"Microsoft has tied the release of both the desktop and server versions of 64-bit Windows to the release of Windows Server 2003 Service Pack 1, which has itself been pushed back.
The software maker said the "technology exchange program" will allow customers to feel secure in buying x64 servers today, pointing out that such servers can offer a 10 percent to 30 percent performance enhancement running existing 32-bit software.
"We see (that) the x64 architecture is, over time, going to become the dominant platform for the server market," said Dennis Oldroyd, a director in Microsoft's Windows Server unit. Oldroyd said the technology-exchange program announced Friday was only for the server OS."