In my article http://blog.ganser.com/975 I described the update from the first version of vCenter Server Appliance 6 to the Update 1. The update needs to connect an ISO image and CLI commands to be installed.
In vCenter Server Appliance you could go the same way or update via Webinterface.
On January 22nd VMware Release Notes added a hint, what to do if the installer stuck at 70%. Read more at the end of my install steps.