We are looking forward to Service Pack 1 for Windows 7 and Windows Server 2008 R2. There will be no changes. The Service Pack will mostly be the collection of past hotfixes and patches.
But we get two new features for Windows Server 2008 R2 with Service Pack 1.
RemoteFX and Dynamic Memory.
RemoteFX means, that you will have enhanced graphics features in virtual sessions with Remote Desktop like you have on physical hardware. More here.
Dynamic Memory is a feature in Hyper-V. You will be able to move part of memory between virtual machines or add and reduce memory during operation.