SMD Software is offering a Group Policy Health Cmdlet that allows you to quickly retrieve status of Group Policy processing on a single machine, all machines in an OU, or all machines in a domain.
http://sdmsoftware.com/blog/2008/12/group_policy_health_cmdlet_now.html
Pretty neat.
You download an MSI which installs the cmdlet for you. Then you just need to use add-pssnapin to add the snapin.
I just ran it here and it runs well!