Today I passed the 70-417 - Upgrading Your Skills to MCSA Windows Server 2012 exam. Building on the studying for the MCITP: SA / MCSA Server 2008 made this exam a little bit easier but I had previously underestimated the amount of new additions and changes in Server 2012.
There are a lot of great enhancements including Powershell v3 (also avaliable on 08 now), improvements to system management, especially remote/centralized management through Server Manager and other tools. There are great features related to Hyper-V and storage management including shared nothing live migrations of VMs. Some time in the near future I plan to make a list of my favorite Windows Server 2012 features.