I take a long-term view of 3D printing.
Not the stupid journalist swoon line of Everyone Will Print Everything Soon. Everyone needs to print their own iPods in the future just about as badly as everyone needs to print their own grainy ABS miniatures in the present. I don't see a demand for it, I don't see a benefit, and I don't see it happening.
So I should say: I take a long-term view of owning a 3D printer.
Like a welder or a sewing machine, there's an enjoyment in keeping crafts alive. There is an eventual return on investment in the equipment itself as well — perhaps over more than one generation. And the mere fact that plastic printers, CNC mills and laser cutters are now being designed with affordability and openness as the first motivation is awesome. I think this means a lot of good in education and economic development (both in overbuilt or underbuilt economies).
It's been interesting to see what people are sharing and printing on Thingiverse. A majority of "things" currently available there for 3D printing are either: limitless small printer kit modifications such that one wonders if the goal of assembling a 3D printer is to spend subsequent weekends assembling it better, or: dis-glorified Happy Meal® toys. Some of the models are terribly cool — who doesn't want to watch a scale B-17 bomber or a miniature London Bridge materialize hypnotically before their very own eyes! — but you know those machines at the zoo where you could put in a bunch of quarters and go home with a hollow elephant, freshly molded from pink plastic?
Gradually, the open source three-dimensional printing community is accreting a collection of replacement pieces, and of speciality parts, and of customizable components with applications beyond printing for its own sake or that of souvenirs. Artists are finding their way within the new medium, too, working wisely within its limitations to create things of real aesthetic value.
It's humbling to be a tiny part of this, to experience its realities firsthand at some level, and to dream about how (perhaps) to make it matter more.
In the meantime…it's fun. And that matters too.