Windows Server 2008 Manageability Feature: Group Policy Preferences: Part 8 Item Level Targeting
One of the features of Group Policy Preferences is to do Item Level Targeting. This enables you to filter out your targets to specific items so that you can implement a Group Policy Preference on a higher Organizational Unit node in the Domain. What this does is a single declaration of your new Policy and have it filter down rather than creating a copy and then applying it to individual OU's. You may also opt to use WMI filtering but sometimes a script can have errors.
An example is to create a filter to apply this preference to this OU but its not logged on a portable computer.