Good uses this could lead to: If used properly, would allow important parts of computers, machines, etc to buisnesses via email. The parts wouldn't be perfect, but would hold out untill better ones arrive.
Mass production of energy-saving devices to help the environment. - Doubtful. Very doubtful.
If incorperated into a mars rover, would allow the rover to create and assemble objects right there on the surface, such as cogs etc to fix itself, provided it is capable of moving those parts around itself. Theoreticly, if it were able to gather and use resources from the planet, turn them into a printable substance, it could become a self-sufficiant creation - the only things it'd need is commands and instructions from scientists on earth. Unfortunatly, verrry unrealistic, and won't happen for a long time.
Bad uses this could lead to: Not much, really. It's not that advanced in terms of technology, just clever. Anyone who thinks that this will quickly become Ai driven, self reproducing robots is very misguided. At the moment it is incapable of printing small circuit boards, and can't work with conductive metals anyway, meaning that the 'self replicating' aspect is only true for the body of the machine, not the technology driving it.
It's accuracy is rather shot, and untill the technology gets good enough to work in microscopic sizes, it won't be able to print anything near what we would consider current computer technology. Now, you can run a spaceshuttle off the equivelant of 10 old BBC computers, but untill this technology gets microscopic; any computers capable of I-Want-Independance AI would take up the majority of my school in terms of space. Not perfect for killing machines.
Nanobots obviously suffer the same problem.
No, we're far more at risk of normal IWIAI or hand-made nanobots than self-regenerating ones, at least for the next 20 odd years, i'd say.
Dosn't particually excite me. Id' prefer a normal 3D printer. However, if I can get all the parts to build one of these (and I know where I can look), I might have a go.