Mouse on the Xbox 360?

Conventional wisdom is that you can't use a mouse on the Xbox 360 (you can use a keyboard though). XNA Game Studio claims not to support it for example. (has anyone tested it? I should probably ask on stackoverflow)

However, this support page claims that "Most USB mouse devices and USB keyboards" ... "are compatible with the Xbox 360".

Also, the Microsoft Wired Desktop 600 Keyboard & Mouse page claims

Mouse Features

• Great for Gaming - Xbox 360 Compatibility
  Perfect for texting and accessing playlists.

Is this for real? Will the mouse do anything when plugged into the 360?

In regards to direct mouse input: No. Mouse input is not supported. Other than plugging it in and trying, I would say it does nothing and can think of nowhere on the interface that it would do anything.

I could find nothing on Xbox Support's site, but did get a response from their Twitter support @xboxsupport

Mouse input is not supported for the Xbox 360

Apparently, Yes. However, I have not heard of direct mouse input without some sort of interface between the mouse. Two products I've heard of that accomplish this:

• XIM3 seems to be the latest one released. There is some news although it seems it's out of stock. The Amazon reviews on it seem fishy.
• A company called XCM makes a line of accessories called XFPS.

I have no experience with either of the above.