I don't think there is any doubt that virtualization of servers is going to become the norm. This is especially true with Linux-based systems. Xen is one of the virtualization technologies I like the most. Because of the way it interfaces the virtual server to the hardware in a very direct way, it's very fast. It does lose some flexibility that other virtual servers enjoy, but I think it is a good trade-off. Also, Xen is great for moving between virtual servers. You can copy a virtual server to another server and switch in real-time between the two. That can be very important if your system has to be up all the time.
The one problem traditionally with virtual servers has been the difficulty of setup. Virtualization not always an easy concept to work with. XenExpress is both free and made as simple as possible. If you have a spare computer, give it a shot.