Microsoft has released first Release Candidate build of Service Pack 1 for Windows 7 and Windows Server 2008 R2. As the Service Pack 1 has entered Release Candidate Phase you can assume that final build is just about ready to be released.
Windows 7 SP1 doesn’t comes with any new features build in. The release basically is just a collection of previously released updates and hotfixes. You have to uninstall any of the previous version of service pack from system prior to installing the latest Service Pack.
What Windows Team says about Service Pack 1 on it official Blog Post.
Windows 2008 R2 SP1 has some new features in it’s bag like Virtualization technologies, Dynamic Memory and RemoteFX. The final build is expected to be released in first quarter of 2011.