I'm a 3D modeler, I've been working with 3D for over 20 years. I've YET to see a useful home-model that isn't just "look - I - printed - a - stock - model - ma!" tech demo. You'll actually be better off with a good CNC machine if you want to make prototypes on the cheap.
We are an electronics company who have a makerbot and a big ass CNC mill (and some manual lathes).The makerbot gets used a couple of times a week by engineers making jigs, or prototypes for form fit and sometimes function. The CNC mill rarely gets used, as it takes a lot more skill and effort to use.
So while I find the concept was overhyped for consumer use, it does find niche uses in businesses that actually need to design and make stuff.