Yes, I have it! Probably one of the first here in The Netherlands. As part of a PoC (Proof of Concept) I'll be doing some testing and preparing demo's on x64 based Windows environment. According to the readme, Microsoft suggests one needs or prefers??? Windows Server 2003 R2 in order to run MPS 4.0 for x64 (see below). I'll do some testing whether it's just a suggestion or also a requirement, since I happen to have latest beta of Windows Server 2003 R2. I'll post my experiences later.

Readme for Citrix Presentation Server 4.0 for Microsoft Windows Server 2003 x64 Edition

Early Release

June 2005

Introduction

Installing the Early Release Software

System Requirements

Microsoft recommends the following:

• Minimum CPU: x64 architecture-based computer with Intel Pentium or Xeon family with Intel Extended Memory 64 Technology, or AMD Opteron family, AMD Athlon 64 family, or compatible processor (Windows Server 2003 R2 Enterprise x64 Edition supports up to eight CPUs on one server)
• Minimum RAM: 512MB
• Multiprocessor Support: Up to eight
• Minimum Disk Space for Setup: 4GB