SQL Performance

To Virtualize or Not To Virtualize that is the question.

Technet
http://blogs.technet.com/b/aralves/archive/2010/05/28/new-white-paper-high-performance-sql-server-workloads-on-hyper-v.aspx
http://blogs.technet.com/b/sqlman/archive/2010/06/16/sql-server-virtualisation-improvements-with-slat-in-intel-and-amd.aspx

Hyper-V
http://download.microsoft.com/download/E/9/D/E9D82F8F-759C-49B7-BD70-5BAAA7F5E477/Hyper-V%20is%20the%20best%20virtualization%20solution%20for%20SQL%20Server%20(Final).docx

AMD
http://www.aimpublications.com/smp-10_TTAMDSQL.pdf

VMware

http://www.vmware.com/files/pdf/sql_server_virt_bp.pdf

Third Party "2 cents"
http://test.sqlserverbeta.com/LinkClick.aspx?fileticket=zGQQIL4R3sA%3D&tabid=86&mid=440

http://whitepapers.businessweek.com/detail/RES/1280165334_68.html

http://stackoverflow.com/questions/149318/virtualized-sql-server-why-not

Answer:  It depends :)