Reserved to share pics/cost/stuff I get made and how I had to tweak files for 3D print manufacturability.

Ehh, 3D printers are a pain in the rear end. Royal pain.

Trying to print anything that takes a longer time means it will break sooner or later and you'll get a half-finished part.

Granted, we're using home-made older designs of 3D printers, but seriously... the tech is not ready yet, plus the material choice is very limited.
You need different nozzles and heating systems for various plastics.

CNC mill is way better and way more versatile, also much more expensive.

Funny, Centric (my other company) was the marketing agency for 3D Systems in their earlier years (1993-7), and my business partner in Centric was the head of their marketing department. So, we know a thing or two about stereolithography, which is a high-res, high-quality, very messy, toxic, and slow way to make parts. We also launched their Actua product, which was the first raster-based additive 3D printer--and holy crap did it have problems--clogging, soft material, etc. We also did some work with a company that was making metal parts with sonic welding. That didn't go very far, for many different reasons (not least of which was the sound, the sound, holy crap the sound.)

Today, 3D printing is one of the darlings of the tech world, with people promising all sorts of wacky things like printing household items from downloaded designs. Yeah, well, we're getting to a point where 3D printing can be truly useful, but I wouldn't plan on printing your own cellphone anytime soon. Most of the press is about the cheap 3D printers, the ones that use melted filament to build parts. But there's really a VERY wide range of 3D printing tech out there, and it's being used in some surprising places:

Filament: builds parts with melted plastic filament, with middling-to-poor resolution. This is great for plastic figurines of your cat and such (no, just kidding, actually there are some very good uses for this, and it can build some very good parts with internal latticing and such that really isn't feasible to produce any other way.) A friend in the entertainment specialty costume biz has a couple of these machines for rough protos and such, as well as a stereolithography machine that is used for "real" production.

Wax raster: Builds wax parts with a raster printhead similar to an inkjet printer. Used to make wax masters for investment casting. You'd be amazed at how many of these are running around in the jewelry business. That $15,000 Tacori engagement ring you just bought? That was cast from a 3D-printed wax master.

Stereolithography: uses UV lasers to cure liquid resin--this is the granddaddy of all the 3D printing tech--and can make very finely finished parts with high resolution. The catch is, the resins are expensive, toxic, and not a lot of fun to deal with. Fun fact: many of the parts of the Loki costume in Avengers, as well as all the parts of the Spider-Man outfit are now stereolithography, because they are interchangeable and provide a consistent dimension as opposed to silicone molds. It's not uncommon for them to build 12-40 complete suits for a movie, so this tech is perfect for short-run production. The material is hard, solid, and does not delaminate.

Selective laser sintering (SLS). Another oldie. This one heats metal powder to near-melting in an inert nitrogen atmosphere, and uses a laser to selectively melt the powder to produce metal parts. Wowzers. Has finish problems. Needs tanks of nitrogen. VERY expensive. NASA is testing using this to print rocket nozzles right now.

Bottom line, there's a lot of different 3D printing tech out there, and it's being used in a lot of different places. I agree it's oversold right now, and it is a pain in the ass, and I have seen some spectacular screwups from all the technologies. It's definitely not a plug-and-play technology. It's definitely not like buying an Epson printer for running some photos. However, I'm actually pretty thrilled to see it being used in the Alpha Dogs, because it promises the ability to create a cup with physical properties that are not attainable with any other means (as you've probably seen, the AD cups are latticed internally, for a product with very light weight and very high stiffness.)

As with a lot of things, we'll see where this tech takes us. But until you've used a 3D printer, I wouldn't start getting any utopian ideas about downloadi ng designs for usable products and forgoing the trip to Home Depot or Amazon.

I built a desktop CNC router a while ago...really fun stuff.  I posted pics/vid of it on HC a little bit ago:

http://www.head-case.org/forums/topic/477-diy-amp-and-such-build-gallery/#entry594383