My company has a series of products that use Unity3d. So our customers are required to install the Unity Web Player. We constantly are asked to indicate computer specifications which is an important question for most as they are schools. All the Unity web site spells out is operating system. I'd love to have the sort of details that Virtools lists for their product: Is this level of detail available for the Unity Web Player??
The download page contains the minimum specifications. How close they are to your application though totally depends on your application. The more visual effects you use and "enforce" to be present, the higher the requirements etc