Ward Ralston has a post outlining some of the improvements in the network stack of Windows Server 2008 compared to previous versions. He talks about a 45x improvement in file transfer time to copy a 10.7GB file from one data center to another. Not too shabby!
Of course, you will also want a new, fire-breathing database server to run Windows Server 2008 on when it RTMs… One good candidate is the new Dell PowerEdge R900 with four Quad Core X7350 Xeon, 2.93GHz, 8M Cache,130W, 1066Mz FSB and 64 or 128GB of RAM. This is the new Tigerton Xeon based server from Dell.