Microsoft has posted a little bit of light reading, a document titled Changes in Functionality in Windows Server 2008 R2 that outlines exactly that, the differences between the R2 release and the original 2008 release. It only weighs in at 1.1MB and 211 pages. You can grab it from the Microsoft Download Center in Microsoft Word format or browse the document online through Technet.
Topics such as new features in Active Directory, DNS (including DNSSEC), Group Policy, iSCSI, IIS, clustering, Windows Deployment Server and many other elements are all covered in great detail. If you’re looking at a server wondering if you’d see any significant benefit to upgrading, other then getting the latest guts of Windows, this is a helpful guide.
Windows Server 2008 was released in February 2008, followed by R2 which was released in October 2009. R2 is Microsoft’s first 64-bit only operating system release and is based on many of the same core programming as Windows 7.
Windows administrators, mark your calendar for the drop dead date to get those old servers upgraded. Microsoft has outlined July 13, 2010 as the date Windows 2000 will no longer be supported by Microsoft. There are already a variety of security threats in the wild where Microsoft has said they will not be releasing updates to protect Windows 2000 because they say it is not feasible. After next July, no support or new updates (except for online self-help) will be available.