If you didn’t know it yet, VMware announced a while back that future releases of VMware will not include the “traditional” ESX Server. From their site:“VMware vSphere 4.1 and its subsequent update and patch releases are the last releases to include both ESX and ESXi hypervisor architectures. Future major releases of VMware vSphere will include only the ESXi architecture.”
If you are in a “24/7/365” shop then the applications running in your private cloud should currently be in virtual data centers (vDC) that are contained in DRS/HA clusters and the migration can be completed with no downtime to the applications. However, there are still other systems, such as development and test systems or possibly some minor infrastructure services applications that may not benefit from vSphere’s availability features. I know many people have scheduled outages, shutdowns, etc. during the upcoming holidays. It may the best time to migrate to ESXi.