The DFS-N test team has completed some extensive Performance and Scalability testing and we wanted to share some of the results.

It includes results on standalone namespaces, "2000 mode" domain namespaces and "2008 mode" domain namespaces, under Windows Server 2003, Windows Server 2008 and Windows Server 2008 R2. 

Check the post by Marcello Hasegawa at http://blogs.technet.com/filecab/archive/2009/08/22/windows-server-dfs-namespaces-performance-and-scalability.aspx.