I received a 3d printer last week, at work. I ordered it to try and make some oilfield equipment models. My expectations in truth were low, the printer is a cheap hobbyist unit (Makerbot Replicator 2). After using it for 2 weeks, I am very impressed. The mechanical properties of the PLA plastic used are much better than expected, and there are things you can make that would not be possible with any other manufacturing process - eg. objects with an internal 3d honeycomb structure for great strength and lightness.

I think the technology can already disrupt such industries as hardware shops, spare parts warehouses, hobby shops and of course industrial model making. In the future I expect 3d printed concrete buildings, and mainstream consumer goods.