CItrix has released a nice guide how to configure Windows 2008 R2 to be at it’s best for desktop virtualization with XenApp 6.0 and XenApp 6.5.
When considering desktop virtualization with Citrix FlexCast technologies, one method for delivering services to end-users is through the use of hosted shared desktops using Citrix XenApp. Hosted shared desktops can deliver a locked down, streamlined and standardized environment ideally suited for task workers where personalization is not required. Delivering hosted shared virtual desktop requires proper planning and configuration to maximize the scalability of server resources while providing users with an optimized and functional desktop environment. This document outlines optimizations for XenApp 6 on Windows Server 2008 R2 to meet these goals.
These configurations typically add value by enhancing the user experience and increasing system performance. For example, some of the changes optimize the user experience by enabling faster logons, reducing unnecessary prompts, and quicker screen updates. Others optimize performance and increase scalability by reducing unnecessary processor, memory, disk and network usage.
However, certain modifications allow for greater scalability but at the cost of the user experience. As many organizations will demand a user experience similar to the traditional desktop, care must be taken when applying optimization settings. Many of these settings are identified within the remainder of the document.
You can download this guide here.