I'm preparing for my 70-646 Windows 2008 Server: Server Administrator exam at the moment and I am shocked at how much of the material is revision. It's actually quiet boring having to study the same stuff all over again for the third time. Some of this stuff was covered in two Windows Server 2003 exams and now I'm studying it again. Sure, I could skip over all the revision, but there are minor changes strewn throughout. It makes preparing for the Windows Server 2008 exams a little more tedious then it was for Windows Server 2003.
Maybe MSFT should have combined the 646 and 647 exams into one exam that covers all the new topics. Then make this exam available to MCSA + MCSE certification holders only.