The technologies of 3D-printing/rapid prototyping are pretty cool and they are making progress but as for actually making spare parts and every day objects that you would ordinarily buy through conventional supply chains, retailers are not yet all that nervous. Many of the systems use plastics, ceramics and even cement which are useful for some applications but many spare parts and other components require the strength and heat conductivity of metals. So a system that could create metal objects layer by layer would enable a lot of new manufacturing processes.
In addition to using less energy and having far less waste material to recycle than traditional machining of metal, not to mention working without cutting fluid, this system allows things to be made which would be impossible or very complex with current technology. A solid metal part with voids inside them to make them lighter is possible. You could print an object with an internal honeycomb structure for high strength with less material. If you currently want to do that you need to create the outer and inner structures separately and join them together.
The article says that two metals may be used either to create an alloy during fabrication or to embed one metal inside another. But I can’t see why future systems should be limited to two metals. It also sounds like glass can be deposited via the same technique but the proposed application of embedding an optical fiber in a metal part sounds to me like the fiber would need to be fabricated separately and laid down as the object is made. The creators are hoping to make a version of the technology that is small enough to have on the International Space Station. Other isolated locations would also benefit from not having to have as many replacement parts on hand. It sounds like quite a spiffy technology.