Here is some information from the Microsoft System Center Virtual Machine Manager Beta 1 FAQ on the Self-Service feature which allows IT Pros to pre-authorize VMs so that users can self-provision.
Virtual Machine Self-Service
What is virtual machine self-service?
Virtualization is commonly used in test and development environments to enable frequent provisioning and teardown of virtual machines. These tasks are easier with virtual machines than with physical hardware. Virtual Machine Manager Self-Service allows administrators to delegate these tasks to users. The administrator can control the configuration of these virtual machines by limiting the templates from which users can create new virtual machines. The administrator can limit the set of hosts on which users can create virtual machines.
The self-service user is presented with a Web page that enables virtual machine provisioning within preset controls. For information about configuring Virtual Machine Manager Self-Service, see Getting Started with Virtual Machine Manager at http://go.microsoft.com/fwlink/?LinkId=69928 <requires Passport or Windows Live ID signin, and Beta 1 FAQ registration).
What rights and permissions do self-service users need to manage their virtual machines?
In Virtual Machine Manager Beta 1, users must have local administrator rights and permissions on their virtual machines if the virtual machines are not joined to a domain. The local administrator password for any virtual machine the user creates is set by the Virtual Machine Manager administrator at the time the template for that virtual machine is created.
In addition, to install the Virtual Machine Remote Control, self-service users must have local administrator rights and permissions on the computer they use to access the Self-Service Portal.
Do I need to use the self-service portal to manage virtual machines created by self-service users?
No. Administrators can manage virtual machines by using the Administrator console.
After users have created their virtual machines by using the Self-Service Portal, they can manage them through the Self-Service Portal or in several other ways. If their organization allows it, they can use Remote Desktop, Terminal Services, or the Administration Web site in Virtual Server 2005 R2.
To use Remote Desktop to access virtual machines, the administrator must enable remote access on the template and ensure that appropriate permissions are given to the user (or group).
How many virtual machines can self-service users create?
In Virtual Machine Manager Beta 1, there is no limit on the number of virtual machines users can create from the templates the administrator provides them. However, they can manage no more than 20 by using the Self-Service Portal. If they create more than 20, they must delete at least one of their existing virtual machines to manage the new ones.