It is stale news to the IT pro world that Microsoft has released the Service Pack 1 for Windows 7 and Windows Server 2008 R2 recently. The service packs can be downloaded here.
There were no notable new features being added through to Windows 7 Operating System by its Service Pack rather there were some enhancements to certain existing features were done. On the other hand the Windows Server 2008 R2 Service Pack has some new features being introduced, to name a few
1) Dynamic memory
2) Remote FX
3) Enhancements on the Direct Access feature
The service packs are a major update released by Microsoft and it is recommended that it to be tested before being deployed. If you or your organization would like to temporarily prevent installation of Service Pack updates through Windows Update you can use the Windows Service Pack Blocker Tool Kit provided by Microsoft (which can be found here) in order to prevent it.
To find out more on the Service Packs it is advisable to read the Notable Changes document & Release Notes documents which can be found here along with the deployment guides.