I ran my first upgrade today to from Windows Server 2008 SP1 to Windows Server 2008 SP2. The installation was for a domain controller running in a virtual (Hyper-V) and it ran for approximately 1 hour and 20 minutes. At this point it appears to be working without issues. A quick video of the upgrade (less than a minute) is attached to this blog entry to give an idea what the process looks like.