Pretty much everything I do right now lives on a protoboard till it gets dead-bugged. I don't do any PCB design at all since everything in my workshop is extremely simple. I do however LOVE the asthetics of a PCB and plan on keeping a close eye on this designline if only for the visuals!
We see a lot of different type of PC boards here in my day job. Of course, standard FR-4 is the most common. Flex boards show up now and then, as do rigid flex. Every now and then an aluminum PCB comes in. These are usually small board for high-power LEDs.
High layer counts are becomming more common - I've seen as high as 30. Those ones are pretty hard to do.
It's unlikely that there would be a low cost tool to make PCBs using the 3D printing approach since you would need to print an insulating substrate followed by (or combined with) metal. All the low cost 3D printers I know about can only do plastic...
I have seen tools that used a CNC approach where you start with copper-clad PCB blanks and the tool cut lines in the copper to generate spaces between the traces. I think they were limited to simple designs with larger traces. I haven't heard of any recently but then I haven't looked....
Around 1990 there was a promising attempt to do this by Ariel Electronics (California), which created a gadget called the Circuit Writer which extruded conductive plastic wires onto a substrate. I actually visited Ariel and saw a Circuit Writer working. I don't think the technology got anywhere, but maybe it was just ahead of its time and with newer 3D extrusions this could be done practically. For more info, Google "ariel electronics circuit writer".
@_hm: I am wondering, is there low cost tool for 3D prinitng of PCB to get them faster and at lower cost in your home?
I have a couple of friends who make their own PCBs -- I remember once chatting with one of them about a small project idea in the morning, and he called me in the afternoon to say that he'd made a prototype PCB and one populated with components was already in the post to me. I will ask him if he woudl be interested in posting some articles on this here on PCB Designline.