Just a note to self, based on the success from the info found at http://virtuallyhyper.com/2012/07/installing-kvm-as-a-virtual-machine-on-esxi5-with-bridged-networking/ (Which has a much more detailed description - so, if unsure, go and read there!)
1) ESXi 5.0 has the nested virtualization support but it is disabled by default.
SSH into the ESXi host and add the following line to /etc/vmware/config:
vhv.allow = TRUE
2) The guest config also needs edits to enable the nested virtualization. Add the below lines to the .vmx file:
Overall, when using the 12.04 in a canned version, things are pretty good. So I upgraded my workstation laptop, which is running a more customized install - fluxbox as a window manager, with a minimalist window theme. "fixed" is not necessarily a bugfix, but a fix from the functionality point of view, sometimes with slight tweaking that I deemed acceptable, so technically it is a union of "fixed" and "worked around".
A list of various "interesting" things I have encountered.