One of the big pushes in Server 2012 is the use a Server Core installation instead of the full GUI install. Microsoft have put a lot of effort into encouraging administrators to use PowerShell as a core tool for day to day administration of servers, which is why is seems a bit strange that a Server Core installation boots to a traditional command prompt instead of a PowerShell prompt.
To change your Server Core installation to launch PowerShell instead of the normal Command Prompt is a simple registry change.
From the Command Prompt run Regedit
Navigate to HKLM\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
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The highlighted Shell dword is what we need to change, so double click on that and type in powershell.exe
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Click Ok and close the Registry Editior.
When you reboot the server you will now have a PowerShell prompt.