Maybe a bit of topic but emBoot release version 2.5 of their product, this is the mail they dropped me:

Our netBoot/i v2.5 diskless iSCSI boot solution for Windows and Linux (now including support for Windows Server 2008 and Windows Vista) has shipped (read the Press Release).

What’s New in netBoot/i v2.5?
• Supports Booting (Physical or Virtual Servers) Windows XP2000, Windows Server 2003/2008, Windows Vista Enterprise, Red Hat Enterprise Linux (RHEL), and SUSE Linux Enterprise Server (SLES)
• Enhanced Shared-Image Support Including Persistence: Boot multiple clients from a single read-only image and maintain individual user’s settings & data
• P2V, V2P, V2V, P2P Migration Capabilities Across dissimilar hardware and Microsoft or VMware virtual machines

Try netBoot/i v2.5 today – free evaluation available

netBoot/i Scalability Demonstrated
We are often asked about the scalability of our iSCSI boot solutions. To respond to these questions we’ve provided a general Capacity Planning Guidelines White Paper. One of our Premier Partners recently put these guidelines to the test in a live customer demonstration project – with impressive results. This diagram on our website presents an overview of the demonstration configuration consisting of:
• 200+ Windows XP workstations
• All workstations booting from a single shared iSCSI boot image
• A single netBoot/i Server supporting all 200+ clients
• A 10/100 mbps client network infrastructure
In this case the customer was doing something that few others have attempted, so they insisted on a live demonstration to verify the scalability of netBoot/i in a shared boot environment. The demonstration was a great success and the customer is planning a deployment of over 1500 workstations in the coming year using an expanded version of this architecture.
Another diagram further illustrating a similar generic shared boot-image configuration for Windows XP is available here. Please contact us if you’d like to learn more about the possibilities of shared iSCSI boot images and write-persistence.

Imagine this in a combination with VDI, just 1 image to maintain just like Citrix Provisioning Server.