The Microsoft Natural Ergonomic 4000 arrived at home today, and I am very pleased. One nuisance: I have a dual boot Ubuntu Linux/Windows PC sharing a monitor, keyboard, and mouse with my primary notebook through a KVM switch. It turns out that the new keyboard is incompatible with the KVM switch. The KVM switch expects a PS/2 connector, and the new keyboard is USB. I have a couple of working USB-PS/2 connectors, which I was using with the previous keyboard--and the new keyboard does not work with it. I have searched a bit, and discovered that I am not the only person with this problem.
I have a spare flat panel monitor, and the old keyboard, but it seems a bit absurd that this doesn't work. Perhaps I need to buy a KVM switch intended for USB connectors. (The PS/2 connector is so 1980s now.)