Yeah... can't wait until RTM...

The update "provides improvements to security, stability, performance, user experience, forward compatibility of configurations, and the programming model."

Update for Windows Server 2008 x64 Edition (KB950049)
As written in the KB article "This package includes the following items:

• Updated version of Hyper-V technology
• Updated version of the Hyper-V Manager console and of the Virtual Machine Connection remote connection tool for x64-based versions of Windows Server 2008
• Updated version of the Integration Services for the following operating systems:
  
  • Windows Server 2008, x86-based versions and x64-based versions
  • Windows Server 2003 Service Pack 2 (SP2), x86-based versions and x64-based versions
  • Windows Vista Service Pack 1 (SP1), x86-based versions only
  • Windows XP Service Pack 3 (SP3), x86-based versions only"

Update for Windows Server 2008 (KB950049)
As written in the KB article "This package includes an updated version of the Hyper-V Manager console and the Virtual Machine Connection remote connection tool for x86-based versions of Windows Server 2008."

If you are looking for improvements over RC0 please read the post of Taylor Brown from the Hyper-V test team.