Having once been really into the maker movement, I'll have to mention the fact that for Engineers and hobbyists, the 3D printer is one of the best things that has happened for a long time. 3D printers are
perfect for prototyping and modding. It is extremely flexible, and the fact that you can design the part that you need and have it ready half an hour later makes it easier to create anything. Plus, compared to a CNC router which is commonly used in big corporations or amongst professional makers, a 3D printer is dirt cheap!
Most of the use cases for 3D printing are things that you can usually already get relatively cheaply, or at least more cheaply than the cost of a 3D printer. I do think some of its applications in medicine are pretty interesting.
Medical applications are huge! This is because of the enormous amount of flexibility when printing it yourself vs. having some mass produced part that not quite fits anyone. Think of it like shoes. When was the last time you had shoes that just fit
perfectly? Shoes are always a little too short, or maybe a little too wide. But with 3D printing, you can make the perfect fit yourself! Of course you wouldn't do that with shoes, but apply the same logic to, say a
CAST or an
EXOSKELETAL ROBOT, and we are starting to get somewhere useful.
As for common adoption of 3D printers - Not yet. The technology is not yet ready for consumers, and the fact that, like with Oryx' AT&T hooks, the price of a 3D printer is not justifiable when looking at options like mass-production or plain old craftsmanship.