For those of you that have an MSDN account you can now download the RTM version of Microsoft Windows 2008 R2 SP1 and Windows 7 SP1. The two key features added in Windows 2008 R2 Sp1 are related to Microsofts virtualization technology called Hyper-V, the new features are 1. Dynamic Memory and 2.RemoteFX.
If you do not have access to MSDN the RTM version will be available shortly on Microsoft web site.
More can be found here on those features: http://blogs.technet.com/b/virtualization/archive/2010/03/18/dynamic-memory-coming-to-hyper-v.aspx