Some of the main areas of improvement in Windows Server 2008 R2 are in Active Directory. Specifically :

• Active Directory Module for PowerShell—  Active Directory Module for  PowerShell is a consolidated group of  PowerShell cmdlets which can be used to  manage Active Directory.
• Active Directory Administrative Center—The Active Directory Administrative Center is an AD management console which allows for the management of users, computers, groups, sites, and domains from a single console.
• Offline Domain Join— Windows machines and be joined to the domain, while offline, using an XML file.
• Recycle Bin for Active Directory—Allows deleted objects to be restored from the Recycle Bin.
• Managed Service Accounts—Improves the difficult task of managing service account passwords by automatically updating all services when the service account password is updated.