3D printing and other additive machining processes definitely have their uses, the trouble is that at the moment they're seen (by non-manufacturing people) as a novel solution to just about any manufacturing problem. The choice of materials is quite limited (very limited for home-scale machines), and dimensional accuracy is generally better in one plane than the others. It's an exciting technology, and it is developing very quickly, but it's not the panacea to all manufacturing needs that some press articles would have you believe.
With today's technology I can certainly see some opportunities for cost effective one-off replacement of otherwise unobtainable components, but I wouldn't (for example) consider printing a safety-critical component without fully understanding all aspects of it and the printing process / material.
