Microsoft have just released another Virtualization whitepaper, Microsoft Virtual Server and the HP BladeSystem.  [Naturally] the whitepaper is all about the reducing TCO via the integrated HP BladeSystem and Microsoft Virtual Server R2. 

But I found the following snippet about VDI interesting:

Undertaking a simpler virtualization solution is another way to help control risk before executing a more sophisticated initiative. HP Virtual Desktop Infrastructure (VDI) is an example of a simpler end-to-end virtualization solution provided by HP and Microsoft. A replacement for the traditional desktop configuration model, HP VDI is an integrated solution that includes hardware, software, and management tools. HP VDI builds on Microsoft Virtual Server technology to help provide a complete virtualization solution at a significantly lower cost than alternative hardware/software configurations.

The whitepaper also includes a link to the HP ProLiant server sizer for Microsoft Virtual Server 2005 R2.  The URL requires registration, but try this link.