@SergioSa,
I am running a "nested" config on a single hi-spec gaming machine at home with the following configuration:
WIndows 7 Enterprise with VMware Workstation 9 on top. Inside that I have multiple virtual clusters - presently I actually have 3 x 3 node ESXi clusters running. 4.1/5.0 & 5.1. I am using openfiler as an iscsi/nas target to present them with storage. I also have a domain and PDC/separate Vcenters etc.
The key with this setup is to utilise solid state drives to reduce contention and keep it all moving.
Also I have a couple of 500 GB SATA drives that I also present to Openfiler. That way I can present different storage tiers to storage clusters inside ESXi.
It's quite effective and most stuff works well. There are some things that don't work such as fault tolerance and the Vmware management assistant but otherwise it's a good setup. I did spend a lot of time planning how to layout the disks between windows 7 and the openfiler but now i think I have it down well....
One of my reasons was wanting to run multiple clusters to test replication/veeam etc and also flexibility etc....
I plan to publish more in my just released blog soon regarding this lab setup but am happy to answer any questions until then...