Before you get too excited, realize that the first service pack is largely just a compendium of patches already distributed via Windows Update. That said, Server 2008 R2 users do get a couple new features called RemoteFX and Dynamic Memory. The former provides a virtualized 3D graphical experience for remote users, while the latter gives on-the-fly control of a virtual machine's memory.
The first service pack is also rumored to bring USB 3.0 and Bluetooth 3.0 support as well as enhanced Bluetooth/Wi-Fi stacks, but Microsoft's keeping quiet on that. The company plans to roll out a public beta of SP1 for Windows 7 and Windows Server 2008 R2 toward the end of July.
In somewhat related news, Microsoft has slipped out the third platform preview (PP3) of Internet Explorer 9. The latest build adds support for HTML5 Canvas as well as audio and video tags. ZDNet also talks of "significant performance improvements," citing an increase on the Acid3 benchmark.