I have 3 harddrives in my home computer and today I though lets experiment with software RAID. So I first made some room on my drives and then created a 3 disk wide software RAID partition in Windows. After that I migrated my development virtual machine and started it. The damn thing is flying now! So if you have some room free on your partitions and don't want all your drives to be hardware RAID 0 because of failure then this is a good thing to do to have better virtualisation performance on your working machine.
By the way, I'm using VMWare Server 6.0.3 as host.