There are other virtualization solutions for this matter, Microsoft and VMWare also provide virtualization tools, but the obvious advantage of Virtual Iron is its cost. However, any of these solutions will allow administrators and the like to save on additional hardware costs, because instead of 10 physical servers running continuously, it's possible to centralize 10 virtual servers in one physical server. As the world evolves and processors, ram, storage, bus speeds continue to offer optimized troughput, with better architectural designs and faster speeds at a smaller size, the industry tends to acquire less hardware components and save up for space, energy consumption and hassle by making use of these virtualization techniques.
There are other developments for the near future currently in the virtualization field, one of these developments is to allow to take advantage on just one graphics card to render directx / direct3d content troughout the several virtual machines, so if i were using linux i could easily play a windows game on a virtual windows machine without using the WineHQ emulator. Last time i checked VMWare was working on that and i think it still is, altough it's already possible to have Direct3D screensavers running on a virtual machine.
Regarding network virtualization i think the market still has lots of space left to grow, altough it's possible to use VMWare and others to create small virtualized networks, the ability to virtualize switches and routers, allowing the end user to look to do lab simulations like in real environments, altough possible for small tests, it still leaves much to desire, for more on this topic visit my other blog regarding networks on netprobe.blogspot.com
Thanks for reading.