Recently I had query around documentation that discusses the benefits of running SQL Server in a virtualised environment on modern hardware with SLAT or second level address translation. The below graph shows that (see the solid red line) the relative throughput for hardware with SLAT & Windows Server 2008 R2 (required for SLAT support) degrades very slightly as workload increases. However without SLAT hardware and with Windows Server 2008 the dotted red line shows immediate degradation even without over commit of CPUs.
The below links have further information on the impact of SLAT. So if you are looking at virtualising SQL Server ensure it is on SLAT enabled hardware.
High Performance SQL Server Workload on Hyper-V
SQL Server Consolidation Guidance