Virtual machine software really must be seen as an enabler rather than as a solution in its own right. Customers really need to examine the whole environment to select the hypervisor that is best for them.

Oracle recently released an update to VM Server for X86. The company hopes that the improvements in its user interface; storage and backup performance; drivers for Windows — that have been validated by the Microsoft Server Virtualization Vendor Program (SVVP); and the inclusion of a large number of application templates to improve application integration will help it win business over VMware, Citrix, Microsoft and Red Hat.

Integrated versus best of breed returns as a competitive weapon

Oracle has made efforts to persuade its customers that they should deploy Oracle Linux and Oracle VM Server rather than using competitive products by promising that tight integration will deliver better performance and quicker problem isolation and resolution.

Microsoft and Red Hat make similar claims about their software stack.

--> Please see the rest on the blog : http://www.zdnet.com/blog/virtualization/oracle-announces-oracle-vm-server-for-x86-release-31/4921 

Please do  keep in mind that ORACLE supports even RAC on VMware, as they would on "real" hardware...