Dealing with Infrastructure as a Software
A Vice President of Infrastructure at a large company once told us something like this, "I like hardware. My hardware hardly ever breaks. The software I deploy breaks all the time. When my data center becomes software, how will I ever have a stable platform?". While the same concern could (and probably should) have once been applied to virtualization, most organizations today are very comfortable with the idea of software pretending to be hardware. The software-defined data center is something a little more intimidating, though. While we've had software pretend to be a CPU for a long time, we've only had software pretend to be a storage array relatively recently. Also, when the storage array goes down, everything tends to come down with it.
However, maybe the bigger question is around software constantly breaking on deployment. Indeed, the most successful OpenStack deployments that we've worked with have all adopted modern software development techniques...