I stumbled across an interesting blurb on Brian Madden's twitter page - Microsoft's Windows Server 2008 R2 will only be available for x64 platforms. This milestone identifies a major shift in CPU architecture standards from x86 to x64. The migration has been a slow one, with the first 64-bit processor released to market in 2000. But before you'll know it 64-bit won't be an option, it'll be a requirement. 64-bit architecture effectively increases the system memory limit from 4GB to 16777216 TB, ten billion times more potential memory space. 64-bit is not natively faster than 32-bit, but a 64-bit system will handle stressed loads and multi-tasking much more efficiently than 32-bit systems. Most 32-bit software can run on Windows x64 systems natively or automatically emulated in compatibility mode using Windows-on-Windows 64-bit (WoW64).

What does 64-bit really mean for you? Of course, every environment will be impacted uniquely depending on applications, drivers, and preparation. Some applications, which I'll classify as legacy applications, were never designed with the intention of using it on anything but a 32-bit platform. These legacy applications may not install correctly or attempt to access data in incorrect locations (the registry for example). Drivers translate instructions from a software level to hardware level, and vice-versa, therefore there is no easy way to emulate drivers. Preparation is the key to success. Problems are inevitable. Here are some recommendations for preparing for 64-bit environments:

1. Hyper-V is $28! Microsoft's cutting-edge virtualization provides an easy and seamless way to virtually create and deploy x86 operating systems from a single Windows 2008 x64 host. This will allow you to support legacy applications in a virtual environment.
2. Print drivers. Many print drivers are not available in a 64-bit format, which means that there is no native way to support remote printing. Microsoft does offer a virtual driver solution in Windows 2008. It requires the client to use Windows XP SP3 or Vista SP1, but there are 3rd-party print solutions which are more efficient and compatible, such as triCerat's ScrewDrivers.
3. Profiles in Windows 2008 are different from Windows XP/2003 profiles. The profiles are somewhat-compatible and the changes aren't significant, but the folder structure is altered which may cause problems for legacy applications. Profile utilities like triCerat's Simplify Profiles can ease the management and transition of profiles.

Upgrading to Windows 2008 R2 proposes some challenges, but the long-term benefits outweigh the short-term investment of upgrading to Windows Server 2008 R2.
Related Links
Microsoft’s Windows Server 2008 R2 Official Product Page
Microsoft’s Migrate to Windows Server 2008 R2 Official Guide
Top 10 Reasons for Windows Server 2008 R2
Windows Server 2008 R2 Beta Download
triCerat on Twitter
Blog: It’s Different on 2008 in 2009!