Lockheed Martin Space Systems has used 3D printing to make a titanium tank.  The effort was detailed in an article here and discusses the experiments to determine if the 3D printed parts could have the same or better quality compared to traditionally forged parts.

“The tank met our customer’s performance standards, with a 55 percent reduction in cost, a 75 percent reduction in waste and an 80 percent reduction in the amount of time needed to manufacture it.”

You can imagine space in a satellite or other spacecraft being tight and the ability to maximize usable space at a cheaper cost would have tremendous benefit.  Getting a part in a fifth of the time is huge as well.  New technologies often show up in the space program or national defense first, so it makes sense that a company like Lockheed would be an early adopter.