Server virtualization has revolutionized the way we deploy systems in our data centers. It has sparked a gold rush along the way, creating outlandish wealth. It has also left a wake of destruction, and it very well may cause catastrophic failures in a lot of shops.
It certainly is going to raise blood pressure and cause hair loss among admins.
The Good Parts: Server virtualization lets you bring a virtual machine online in minutes, gets you enormous utilization gains on your hardware, and enables mobility unlike anything we've ever seen before.
The Bad Parts: Server virtualization has created an on-demand expectation from the business that hasn't been fully vetted yet. Mobility, specifically the ability for a virtual machine workload to take on migratory attributes, creates massive performance problems, not only for that workload, but for all the other workloads on the same physical kit. Worse yet, you can't see it. You only know it when the phone rings and everyone is screaming at you.