It MAY be possible to boot a USB disk that is pre-installed with Mikrotik ROS with vmware esx. I am working on it and will revert. Has anyone else managed yet?
Not on ESX, not using USB, but I have successfully tested the 4.0 beta on vmware w/s 6.5 (probably, the latest one). It runs damn fast with massive performance. I have also put a live 3000 user traffic on top of that. It rocks.
I do not have ESX but had I had that i'd run all the mikrotiks on that. Its blazing on VMs.