I have printed a lot of quads though mostly triangles.

During the Dutch Design week several things around 3D printing were presented:
- a modified Ultimaker 2 for biocomposites (think mushrooms, spores, compost fibers)
- printing Filaflex wearables on a Prusa i3 by Perflex company
- detailed connector systems for applications like shelving and lights, also printed with surprising quality on the i3
- anatomical models showing heart complications
- a custom build machine for patterning felt and other fabrics using custom shaped heat stamping hot ends.

Also, some company printed an entire motorboat hull using regular polymers. This showed 1. it is not very durable 2. it is not as water/weatherproof and 3. production time will be very high. So all in all this will only be suitable to produce very small series to make up for long labor and tooling costs of traditional processes. But you will still need to manually finish and reinforce the parts. It is definitely possible though. Also a US company is creating wheel covers for one wheels using 3D printers with great success.