Prior to the os launch Microsoft has released two updates. One is an updated camera codec pack and the other is a 175mb compatibility and stability update:

Notes
•The Microsoft Camera Codec Pack update adds the ability to view many device-specific file formats to Windows.
•The update enables supported RAW camera files to be viewed in Windows Explorer and in Windows-based applications that use Windows Imaging Codecs.
•The Microsoft Camera Codec Pack provides support for many device formats. For more information about the supported device formats, see the "More Information" section.

Update information

Improvements
This cumulative update includes the following performance and reliability improvements:•Increased power efficiency to extend battery life
•Performance improvements in Windows 8 applications and Start screen
•Improved audio and video playback in many scenarios
•Improved application and driver compatibility with Windows 8
More information on the updates can be found here:

Windows 8 Client and Windows Server 2012 General Availability Cumulative Update

An update that adds Microsoft Camera Codec Pack support to Windows 8 and Windows RT is available