Server 2012 includes de-duplication for non-boot volumes that are formatted with NTFS (not ReFS). It runs as a scheduled task.
Parallels Desktop 4 doesn't support Server 2012 as a guest (I tried), but VirtualBox 4.2.4 does. In fact, VirtualBox blew me away with how refined it is for a free product. I'm very satisfied with VirtualBox so far.
CHKDSK is enhanced: scanning is done while the server is running and any repairs are attempted at that time; if a repair requires a reboot, CHKDSK only works on the exact problems that were flagged earlier so the server can reboot quickly.
At the Ctrl + Alt + Del login screen, there's a button to show the password you typed in clear-text.
The UI is not pretty, even with the Desktop Experience installed. Navigation is easy though, you hit the Windows key on your keyboard and then start typing just like in Windows 7 to search for what you want. Alt + F4 is the fastest way to reboot. How to navigate the new UI. Keyboard shortcuts.
Active Directory now has a feature called VM-GenerationID so we can roll-back a virtualized domain controller to an earlier snapshot without messing up Active Directory replication.