I am running Hyper-V Windows 8 and VMware Workstation 9.x side-by-side. This is what I did.
1) Made sure Hyper-V role was disabled
2) Installed VMware
3) Re-enabled Hyper-V role
4) Made the following entry in the my vmx that I wanted to fire up to allow nested VMs
vmx.allowNested = "TRUE"
I needed VMware, since the Linux Integration Services capabilities is poor for Hyper-V on Win8. Specifically talking about graphics display. For all Windows based VMs, I use Hyper-V.