vCenter in a VM is fully supported by VMWare. But I would say it also depends on your vCenter services, such as VMware-FT, or Distribution switches. When you are thinking of implementing these services and your vCenter is in a VM, then think of making your vCenter Highly available because these services are heavily depends on the vCenter.

Think of creating a MCSC cluster of vCenter on the local datastore of each host, so each vCenter Node will resides in the local datastore of the ESX Server.