Al Sorenzo has a very interesting article on how to exactly use Group Policy Preferences in an existing mixed Windows Server 2003 / Windows Server 2008 environment. Why are Group Policy Preferences so cool? Because they allow you to do all the things with Group Policy that you want to today but just can’t. Now you can do all of the stuff that you currently need to do in a Login script from Group Policy.  This feature has a huge potential. Over the years Group Policy has become a best practice for configuring environments where possible. Notice the phrase "where possible". Group Policy does a decent job at configuring static settings but just isn’t fit for managing dynamic settings.

Combining the powerful features with this extreme granular filtering options makes Group Policy Preferences an extremely powerful way to manage all kinds of settings. The Logon script could become an endangered species. But wait… there has to be a catch, right? It must be available to MDOP customers only or something like that right? NO! Group Policy Preferences are available in plain Windows Server 2008. Group Policy Preferences support the following platforms:
• Windows XP SP2
• Windows Vista
• Windows Server 2003 SP1
• Windows Server 2008

Al Sorenzo has all the details in his article that tells you how to make Group Preferences work in a Windows Server 2003 / Windows Server 2008 / Vista environment. Read his article here.