I have been using Windows 8 Release Preview as my sole operating system for some time now. Yesterday I upgraded to Windows 8 Pro.
I tried to install from the DVD after changing the Boot option in the BIOS. But it would not boot from the DVD. The message to "Press any key to boot from DVD" did not come up. After trying a few times I gave up.
The I tried the Set Up from inside the system. It started smoothly and upgraded the system.

The only option was to retain the personal files which I exercised.
While it was setting up windows 8, the computer restarted a number of times and the message to "Press any key to boot from DVD" came up.
Activation was automatic.
BTW there is an option to get more features with a new edition of Windows. When I clicked it it asked for a Key. When I gave the key I was using, it said that is not sufficient. What are these new features?