I can't directly answer your specific question, but here's something to think about.
I don't know about 6.6, but I have done all of my testing on 9.3.1, 9.3.3 and 11.1.2.x on VMs. The problem with using this product line in a production environment on a VM is the way the licensing is done. My licensing is per CPU. Because of our method of partitioning VM spaces being what Oracle calls "soft partitioning", I would need to license the product for all 30+ CPUs in the VM cluster. Installing the software on dedicated hardware turned out to be much less expensive.