Thanks to Dugie for bringing this to my attention.  We have just published a document that outlines approaches and best practices for running Windows Essential Business Server in a virtual machine.  You can grab it here:

http://www.microsoft.com/downloads/details.aspx?FamilyID=933b2eb6-f3bb-47c1-a227-13bb2ccc0a94

Here is the abstract from the document:

This document provides guidance for virtualizing Windows® Essential Business Server (EBS) 2008 by using the Windows Server 2008 Hyper-V™ technology. Server virtualization allows you to install Windows EBS software on a single physical server reducing hardware, energy, and management costs. Virtualizing Windows EBS consists of the following steps:

• Choose a virtualization configuration
• Install and enable Hyper-V in Windows Server 2008
• Create and configure the virtual machines for Windows EBS
• Install Windows EBS on the virtual machines

This document covers virtualizing Windows EBS Standard

Cheers,
Ben