I inherited an older Microsoft Server 2008R2 DC running AD/DNS/DHCP taht was converted to a VM. I was having some issues with it but I was trying to wait until we moved to a new circuit and made some other networking issues. It crashed.
I built a new DC with 2012R2- I was able to get everything up and running no problems.
That being said have some quirky issues. There are some people who were experiencing slowness- if I gave them a static ip address slowness went away
I have one server that doesn't seem to resolve to DNS anymore.
i realize that not running dcpromo is not ideal but I did not have an option. Everything else seems to be ok