For organizations that are looking to virtualization for DR, moving fully to virtualization for both your primary and recovery site is certainly going to be more of a challenge because there's going to have to be a lot more roll out at the primary site. There is an attractive opportunity for organizations to look at virtualization for their recovery site and still consider keeping a lot of resources physical at their primary site until something changes in the future.
So in a nutshell, virtualization at the DR site does make sense because there are some benefits to be had there. Virtualization at both sites certainly makes things much easier, but there are benefits even if you just turn to virtualization at the DR site. Those include easier management of the DR site (all the virtualization vendors have tools for managing the server better, for booting servers remotely and reducing the resources you're going to need at your DR site). So there is a tremendous cost-optimization opportunity there if you can consolidate a bunch of physical resources that might not need the same physical resources underneath them. They might not need as much I/O performance or CPU performance in a true disaster, maybe it's just a service that you have to sustain even in a degraded mode. So, you can collapse your 50 or 100 servers onto 10 or 20 servers that are virtual servers at the virtualized host, at a remote recovery site.
Organizations also need to realize that the cost optimization is more than just consolidation, because server virtualization allows you to easily repurpose those resources too, so when you're not using them for DR, you can easily use them for test and development. So boost those systems up and use them for test and development.
If you have a DR site, most of the management frameworks will automatically shut those servers down and bring up another set of servers and failover. If you're using those servers for other purposes, there may be more disruptions than a DR event, but that may not be an issue for you considering the cost optimizations.
The challenge with going from physical to virtual though is that there are sticky issues like compatibility between a physical server image and a virtual server image, as far as drivers and that type of thing go. You also have to deal with I/O on your physical servers. You've got to be a little bit sensitive to how much load you're going to put on a server host when you consolidate 20 physical servers on that host in a DR situation.
You've got to observe your performance load in a production environment so you're prepared to right size your DR environment, but otherwise, it's a great opportunity to use server virtualization for DR.