But ESX as a VM with running VM’s is new. It’s now possible to run ESX as a VM on an ESX server or in a Workstation. See howto http://www.vcritical.com/2009/05/vmware-esx-4-can-even-virtualize-itself/
Read this post before upgrading.
Techtarget.com has released their Top 10 pick from VMware to tryout in 2009. Read it. Fault Tolerance (FT) VMsafe vNetvork Distributed Switch and Cisco Nexus 1000v virtual switch vCenter CapacityIQ vCenter Data Revovery vCenter ConfigControl vCenter Orchestrator vCenter Chargeback vCenter AppSpeed vShield Zones