I have it running as Others - Mac OSX 10.7 64-bit on VMWare Workstation 9.
Downloaded a VMDK with 10.8 preinstalled that worked as a fresh install, you just run it and setup the 1st boot as if you just finished installing.
Have setup the VM with 4 cpus + 16Gb ram, performance is great, everything works. Even updated to 10.8.1.
Just google 'mountain lion vmware', i used the first link to DL + setup.