Microsoft today started delivering Office 2013 Service Pack 1 as well as SP1 releases for the on-premises versions of Exchange 2013 and SharePoint 2013. However, the Office 2013 SP1 release is only for standalone installs of the product, not the versions installed with Office 365 subscriptions: Those SP1 updates will ship with the next rev of updates for those subscriptions.
Office 2013 SP1 improves compatibility with Windows 8.1, Internet Explorer 11 and modern hardware, such as high-DPI devices and precision touchpads. It also provides new apps for Office capabilities and APIs for third-party developers. In addition, Office 2013 SP1 includes all of the monthly security updates that were released through January 2014, and all the Cumulative Updates that were released through December 2013. It also includes all of the previously unreleased fixes that include general product fixes, as well as improvements in stability, performance, and security.
Additionally, SkyDrive Pro has been rebranded as OneDrive for Business, as you'd expect.
If you're using a standalone version of the product, you will get Office 2013 Service Pack from Windows Update over the next 30 days. Or, if you can't wait, you can download Office 2013 SP1 from the Microsoft web site. (Or, for you rare users of the 64-bit version, use this link instead.)
Using Office 365 Home Premium or any business version? If you downloaded and installed the products via Office 365, Office 2013 are kept up to date automatically. Click-to-Run will automatically check for updates in the background, Microsoft says.
If you are using Windows RT (8.0 or 8.1), you will get Office 2013 SP1 starting today on Windows Update. There's no direct download.