My primary domain controller for our company is a Hyper-V virtual server, running on Windows Server 2008 x64. I've upgraded other DC's in the company to Windows Server 2008 R2 over the last 2 years, and feel that the primary should be on the same level or higher than them. No rationale behind that thought, just makes sense in my head.
Regardless, I'm wondering what opinion's are out there for the path to do so. Can I safely run an in-place upgrade to 2008 R2 or 2012 or should I start from scratch and build a new virtual. Obviously the downfall to that is that I would have to demote the current and promote the new one, which has its challenges.