Just browse to the Windows Home Server site and select "Try it for 120 days" on the right hand side of the screen.
If like me you haven't splashed out on buying a Windows Home Server and would like to take one for a spin then downloading the trial is a good way to go. I've seen quite a few of the purpose built devices and have been pretty impressed with them. The idea of a low power server (the one I want uses <38W) that can be configured to wake up my other computers @ night to back them up is pretty appealing. I think the best feature of Home Server is it's ability to accept additional USB connected hard disks and seamlessly extending the logical storage area without me having to worry what data goes where.
I also like the idea of being able to securely "sign in" from wherever I am to access both data held on the server AND control any home automation devices I've integrated with it.
If you're a technical enthusiast who want to buy/build home automation hardware OR if you have multiple PCs @ home then Windows Home Server is worth a look.
The Home Server blog is another good place to find out more.