"Windows 7 SP1 download links are now live for MSDN and TechNet subscribers, so head to your downloads page and grab the updated ISOs. Public availability will follow on February 22nd, and end users will be able to install Windows 7 Service Pack 1 via Windows Update or download an installer.
As we've said before, SP1 won't bring many (if any) visible changes to the average user. In addition to rolling up previously available updates, Windows 7 SP1 introduces some key virtualization and remote desktop improvements.
Subscribers may want to wait until the initial rush subsides -- Microsoft's servers typically get slammed hard when top-tier downloads become available. Otherwise, we recommend downloading with the Akamai downloader. It's working well for us at the moment.