Hi All :
When you installed System Center 2012 Operations Manager , and maybe you find the version is EVAL , like this :
And you need to use right Key to converted from EVAL to Licensed , so you need to use Set-SCOMLicense command.
Run finished , please restart SC2012 OpsMgr Management Server , use Get-SCOMManagementGroup | ft skuforlicense, version, timeofexpiration -a to check result :
You can see the About information to confirmed :
More details , please reference KB2699998 : http://support.microsoft.com/kb/2699998