http://support.microsoft.com/kb/2207548
In some cases you may experience degraded overall performance on a Windows Server 2008 R2 machine when running with the default (Balanced) power plan. The issue may occur irrespective of platform and may be exhibited on both native and virtual environments. The degraded performance may increase the average response time for some tasks and cause performance issues with CPU-intensive applications
Lame!
Michael Ellerbeck 
Thanks for pointing this out. This seems a little ridiculous: “Please note that you may not notice performance issues while performing simple operations. However, applications or scripts that intensively use resources (primarily processor and memory) may exhibit the problem.” So, if you don’t load the server everything seems fine. It just kind of chokes when you actually try to do something… Wow.