I think nanotechnology will be cool, but not as cool as in science fiction (it's not magic after all, it's technology). Universal constructors will be slow (to not overheat by the insane amount of computations required to place individual atoms). The usual manufacturing process will begin with engineering of an energy efficient specialized constructor, then more or less slow construction of the specialized constructor, and then the constructor will churn out the requested goods.

The entire process will, of course, be automated, but if you need something truly unique or if you are bootstrapping extraterrestrial habitat, you'll need to wait.