A couple of years ago I remembered going to a demo and watching Hyper-V crash, but since then a lot has changed. Hyper-V can now do many of the same things most enterprise virtualization software boast about. Live migration, HA, templates, and importing VMs from VMware and EC2 using SystemCenter VMM. The only real hang up is the lack of popularity with the Linux community
The force driving server virtualization is similar to that which led to the development of time-sharing and multiprogramming in the past. Although the resources are still shared, as under the time-sharing model, virtualization provides a higher level of security, dependent on the type of virtualization used, as the individual virtual servers are mostly isolated from each other and may run their own full-fledged operating system which can be independently rebooted as a virtual instance.