In no real order…
Support for 256 cores, because you can never have to many cores. (previously only 64 were supported)
Core parking, this enables Windows to park or suspend cores that aren't in use, handy I am sure in those situations when you have 256 cores! This provides significant power saving benefits.
64 bit only (x64), further driving the adoption of 64 bit computing.
Powershell 2.0, as if version 1.0 was not good enough, we will be blessed with version 2.0. Version 2.0 will also now include a UI for developing and debugging in.
IIS 7.5 FTP improvements, finally Microsoft will provide FTP over SSL and virtual host names for FTP sites, this allows multiple FTP sites that share the same IP address (much like host headers in HTTP)
DirectAccess, seamless, always-on, SSL based VPN solution with NAP support (reminds me of Citrix Access Gateway *cough* *cough* but @ 5% of the cost!) only for Windows 7 users reason to upgrade!
BranchCache, provides WAN optimisation/optimization :-), reduces WAN traffic using two deployment models. Distributed caches content on Windows 7 machines that have previousaly retrieved content and then makes this content available to other clients. Hosted caching is cached at the branch on a Windows 2008 R2 server retrieved data, simple put the Windows 2008 R2 server works on behalf of the client to cache content.
Remote Desktop Services, AKA Remote Desktop, AKA Terminal Services. (Mmmm… Remote Desktop + Terminal Services = Remote Desktop Services marketing genius :-)) New RDP version 7 protocol, Windows 7 Aero support, Direct 2D & Direct 3D 10.1 application support, True multi-monitor support, RDP Core Performance Improvements, Multimedia enhancements, Media Foundation support, DirectShow support, Low Latency audio playback support and Bi-directional audio support. The RDS/XenApp gap closes further!
Hyper-V R2 Live Migration, the ability to shift VMs between hosts without user downtime, comparible features to VMware’s Vmotion or Xen’s Live Motion. While not required but highly (with a capital H) recommended utilises Windows 2008 R2 Cluster Shared Volumes.
Integrated Best Practices Analyzer, BPA advice now available out of the box for all server roles
IIS 7.5 Request Filtering, This will include the filtering features previously found in URLScan 3.1 with a GUI!
.NET framework in Server Core, I am not a big fan of Server Core myself however I know others are and I am sure there are plenty of people out there that will be happy that the .NET framework has made it into Server Core deployments. This extends to ASP.NET and Powershell making this a good solution for web type deployments.
Remote Server Manager, “Server Manager” is a nice centralised management tool, now with R2 it is no longer limited to the local install as this can not be installed to a remote network client.
Active Directory Administrative Center, Say goodbye to Active Directory Domains and Trusts, Active Directory Sites and Services, Active Directory Users and Computers. Say hello to Active Directory Administrative Center, built on top of Powershell and includes the new Active Directory Recycle Bin for those magically disappearing OUs.
TCP offload support in Hyper-V R2 virtual machines, (AKA Virtual Machine Queue (VMQ) and TCP Chimney)
Support for Enhanced Virtualization Capabilities, Support for Nested Page Tables (NPT) and Extended Page tables (EPT) in Intel and AMD hardware. These capabilities improve the performance of translation of memory addresses. Some people have reported up to 2.5 times the number of VMs under Hyper-V R2 over R1.
Integrated RDS and VDI, a single broker is now available to connect users to RDS sessions or virtual machines in a VDI deployment with Hyper-V R2.
Hot Add/Remove VM Storage, ability to “hot add” VM storage both pass through or VHD to running VMs (only available on virtual SCSI controllers)
Cluster Shared Volumes, Enables multiple nodes in a cluster to concurrently access a single ‘truly’ shared LUN.
Expanded Support for iSCSI, Multiple LUNS can be mapped to a single iSCSI target as well as improved iSCSI multipath support and reported performance enhancements.
Remember Windows 2008 R2 (and Windows 7) will be on the streets October 22nd.