I wrote this white paper and it's finally out: http://www.microsoft.com/downloads/details.aspx?FamilyID=2f595e22-c9f1-4376-a8b2-7a7eccd2aba5&displaylang=en.

It basically describes how to run a Performance Testing lab on Project Server 2007 with Visual Studio 2008 Test Edition and a bunch of other community based tools. There will also be an accompanying project on codeplex (http://ps07plt.codeplex.com, but it's still in the publishing process...) with the Visual Studio solution ready to be used as a starting point for your tests. Finally, the white paper presents some reference results from the lab environment that we used.