From Xbox360Fanboy.com : "Allowing the use of a keyboard and mouse (or a Dual Shock) on the Xbox 360, the XFPS has created quite a stir here at 360 Fanboy. Hailed by PC using FPS fans as a godsend and decried by proponents of an equal playing field, it's a potentially controversial piece of hardware. When it comes to first person shooters, the advantages of a mouse and keyboard over a control pad cannot be denied, but is it fair for certain 360 players to have a distinct advantage over others? It's an interesting question, but ultimately the answer lies in how well the XFPS actually performs. We put the unit through its paces and see what it's worth.
Setting up the XFPS isn't difficult at all. Just plug it into your 360, attach a wired controller, mouse, and keyboard to the XFPS, and turn on your 360. Once enabled, the XFPS has a standard keyboard and mouse layout, or you can choose to map buttons yourself. To map buttons, you need only tap the program button, the button you want to map on the 360 controller, and the corresponding button on the keyboard or mouse. For example, to map the shoot command to your left mouse button: tap the program button, pull the right trigger on your control, and click the left mouse button. Done. The XFPS only has two USB slots and the controller takes up one of those, so we're not really sure how you program your mouse and keyboard if they're both USB, though it is possible to use the default scheme. To use a Dual Shock (even a PS1 Dual Shock will work) all you have to do is plug it in. The Dual Shock simply mimics the layout of the 360 controller (minus the guide button)."