Here's a great blog post on why WS08 is called SP1.

http://blogs.msdn.com/iainmcdonald/archive/2008/02/15/windows-server-2008-is-called-sp1-adventures-in-doing-things-right.aspx

I have to agree - Microsoft got it right on this one.  Plus I think there's an added level of confidence inherent in knowing that the same kernel code is running on both our clients and servers.  I suspect this will mean that, in the end, Vista and WS08 are going to be with us for longer than even Microsoft wants to believe.