One of the best reasons for upgrading to R2, is the new account types for managing services. Changing user account passwords being used for running services, scheduled tasks and application pools are often a real pain and consequently, often being skipped. And wouldn’t it be nice if it was handled automatically like a computer account? Well, that is exactly what R2 offers.
Two new types of service accounts are available in Windows Server® 2008 R2 and Windows® 7—the managed service account and the virtual account. The managed service account is designed to provide crucial applications such as SQL Server and IIS with the isolation of their own domain accounts, while eliminating the need for an administrator to manually administer the service principal name (SPN) and credentials for these accounts. Virtual accounts in Windows Server 2008 R2 and Windows 7 are "managed local accounts" that can use a computer's credentials to access network resources.
Read the Service Accounts Step-by-Step Guide for more information.