Thanks for the offers guys - but I don't have a model in mind yet. I was just curious if anyone has machined a MoI model, and if so, what software was used.

Here's a possibility:
http://www.deskproto.com/gallery/reference.htm

By the way - my mill has the rotary axis 90 degrees to the spindle, so I can cut around a cylinder.

Machining has its limitations of course. Just because you can draw a model doesn't mean you can machine it. However, for those who make castings, the latest thermal wax printers have incredible accuracy and can pretty much reproduce in 3D anything you can create. I expect MoI to have a market for this type of application. See:
http://www.2objet.com/Misc/Gallery/tabid/70/AlbumID/393-22/Default.aspx

Ed