I just installed Vsphere 5.1 and Mountain Lion, and the whole thing went exceptionally smoothly. The system is a Supermicro X8ST3-F with 12GB of RAM and a Xeon E5506. Once Vsphere was installed I applied the patch, and used the hdiutil trick posted by Battmac to create the CD image for 10.8.2: "The ISO image must be created from the Lion ‘InstallESD.dmg’ (you can open package contents and browse to the "ESD.dmg located in /Contents/Shared Support/InstallESD.dmg.) Using terminal on Mac OS: hdiutil convert InstallESD.dmg -format UDTO -o InstallESD.iso. This will result in a .cdr file (.iso.cdr). You simply remove the ".cdr" and keep the ".iso" I then copied the .iso to a "local" storage on my ESXi box, and pointed the installer to the iso... " Booted the VM and Mountain Lion installed and is very happy. Many thanks to every here!