I believe there must be logs in /var/log/vmware-imc. If it's not there, there is a big chance that guest customization simply does not trigger for you. The log consists of two files:
- toolsDeployPkg.log is from the Tools plugin which schedules guest customization. It should be always created in case guest customization triggered at least once
- customization.log is normally created as well, unless there was some critical issue which would be visible in toolsDeployPkg.log
Now, customization is triggered based on "customization enabled" flag + some internal "dirty" flags. Those "dirty" flags are normally set when you change "computer name" or any of the NICs (add, remove, change network, etc). I think I saw some issues on one of the old versions where VM without NICs was added with the same "computer name" as in template and customization didn't trigger on the first power on. Although on the latest sources I have it's working fine.
If you suspect that customization does not trigger, you can always trigger it yourself. Just use "Power On and Force Recustomization".
With regards to Ubuntu 12, I would expect password customization code work fine. I believe there were some big changes with regards to DNS resolution. However, it should work for you if you disable Network Manager which I would recommend anyway, since current implementation doesn't play nicely with it.
/Andrii