If you get a “The Deployment Service cannot process the request because one or more validation checks failed”, then know this:
Import-CRMOrganization will fail if the organization already exists. For the import to succeed, you need to drop the organization if it already exists. Wish this was documented somewhere!
Note: If you have already checked to make sure the organization doesn’t already exist, make sure that the “XRMDeployment” webservice is running under an appropriate account. Check this for more information on that: http://blogs.msdn.com/b/darrenliu/archive/2011/04/27/minimum-permissions-required-for-dynamics-crm-2011-setup-services-and-components.aspx (See the section on Deployment Service).