As of today Microsoft offers the KB950050 update for Windows Server 2008 – which means: Hyper-V – the hypervisor of Windows 2008 is now available in the final release version.
“The update to the Hyper-V role provides improvements to security, stability, performance, user experience, forward compatibility of configurations, and the programming model. All users of the Hyper-V role should apply this update. After you install this item, you may have to restart your computer. After you have installed this update, it cannot be removed. This update is provided to you and licensed under the Windows Server 2008 License Terms. With this update, you can now use Hyper-V in a production environment for supported configurations. Please see Windows Server 2008 Licensing and Support terms for more information.”