The problem is the plating; for an idea of current commercial solutions, look at LPKF.
We need a better way of making connections between layers for desktop PCB makers to take off. However, I'm still think that for most hobbyists, assembly is a much bigger pain point (so getting a usuable desktop P&P machine + reflow oven is more important)
IMHO a better approach for rapid prototyping of PCB would be a mini CNC mill, no chemicals involved. However they are a lot more noisier, and PCB dust would pose a problem. Some sort of vacuuming system would be needed to avoid the later (maybe even plug in your home's vacuum cleaner).
I feel the opposite -- the pain is getting (that is, waiting for the turn-around) time of getting the boards made. Soldering up a board only takes a couple of minutes/hours depending on how complex the board is.
The soldering time is miniscule compared to the turn-around time of getting the PCBs made. Assuming that you're truly prototyping, gerbers to FR4 is clearly the bottleneck, because that's usually measured in weeks. It's true that if I need a prototype board right away I can etch, drill, via and solder it up the same day -- but it'll take all day.
If you're talking about something that tastes more like production, then sure, the biggest pain is assembling the (SMT) boards because it'll take you just as long to etch 100 boards than send them out.
@perl_geek: My immediate reaction was that it somehow laid down conductive traces. How might that be done? A conductive ink, perhaps copper particles in some kind of binder?
I thinbk the "Printer" in the name is a bit missleading -- it's more of an etcher -- you transfer the required pattern to the board by hand, then this machine will use/mix the chemicals in the right order / times / amounts along with providing agitation and so forth.
@Perl_geek - The article says the machine etches the board, so I suspect it is standard copper-clad PCB, probably the pre-sensitised type, and the printing process is laying down opaque ink for the traces before exposing it to UV. Or possibly the print head has a UV Laser on it and exposes the PCB where you DON"T want tracks, prior to etching. Joshua has gone quiet, it seems, hope he will tell us more....
My immediate reaction was that it somehow laid down conductive traces. How might that be done?
A conductive ink, perhaps copper particles in some kind of binder?
An "inkjet" that heated copper to a point that, when spat out, it would melt into a trace? (Perhaps making connections between elements of a pre-printed grid, so much less "ink" would be needed?)
Some sort of EDM to cut traces in a similar, but connected, grid?
Do PCBs have to be rigid "boards", or could a flexible wiring harness be embedded in a suitable insulator? That could be laid onto a perf. board for structural support. Just put the through-vias where you know the holes are going to be.