There are quite a few changes in R2 when it shipped and became generally available on Oct 22nd with Windows 7! Below is a link to a master list in TechNet where you can find some really good info!
 
 
       Some of my Favorites are the new Hyper-V 2.0, Powershell 2.0, and the AD changes (AD aministration center anyone?) !
 
 
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