Arguably, even more important than bringing the price of 3D printers down to affordable levels is making them more practical. A commonly cited limitation of 3D printing right now is that they can only fab with one or two materials and can't really reproduce their own circuitry. They're both fair points, I can't argue with them. I can, however, point doubters in the direction of the Rabbit Pronto, a new print head for RepRap-derived 3D printers that is capable of fabbing functional electronic circuitry in addition to structural plastic. The Rabbit Pronto incorporates a 10cc syringe that can be used to lay trails of conductive ink or conductive polymer that do the same thing as etched copper paths on printed circuit boards; this can be done simultaneously with the deposition of layers of structural thermoplastic. This would largely obviate the need to construct separate circuit boards for 3D printed projects; this also means, incidentally, that if you were using a RepRap to print out parts to build another RepRap you could print out the circuit boards as well as the specialized structural components that you can't get off-the-shelf. You'll still have to supply your own electronc components. We can't fab discrete components or chips yet and you'll have to use conductive ink instead of solder to assemble the circuitry but it also means that you won't have to go to the trouble of etching your own circuit boards. Hypothetically speaking you could probably use this print head to deposit layers of any reasonably viscous gel or paste, but you'll want to clean it thoroughly before you do so. You can pre-order two different versions of the print head or a complete 3D printer.
The Rabbit Proto is open source so you can check the meshes and software out of Github if you want to build your own.