My upgrade experienced wasn't particularly smooth.
Preparing Files FAILED with "A reboot is required to complete file operations on '{4934D1EA-BE46-48B1-8847-F1AF20E892C1}'. Reboot the machine, and then run setup again.". Fortunately it did continue when I ran setup again.
Then I had the "Cannot determine the product name registry subkey, neither the 'RegistryProductName' application setting nor the 'CERES_REGISTRY_PRODUCT_NAME' environment variable was set
I had to set the CERES_REGISTRY_PRODUCT_NAME environment variable to "Search Foundation for Exchange" to fix this.
Finally setup waited a very long time for the service 'MSExchangeFrontEndTransport' to reach status 'Running'. This never happened, so I restarted the server, then the FrontEnd Transport started, but then the Transport service would stop shortly after starting. It turned out that the default receive connectors had been modified in such a way that these two services tried to listen on the same IP-address on port 25. I modified the default rule to listen only on a particular IP-address and then both services would start correctly.