[merrillii]

I think your bar is a bit high. Standard milling tolerences are almost 50x higher than what you state. Casting is much worse. The point is that additive printing won't take over the metal world any time soon but it does have some advantages. Try to machine a hollow sphere for example. There are plenty of shapes that can't be traditionally machined.

[Animats]

Yes, milling to 0.0001in tolerance is rare, although possible on some machines. 0.001in is not unusual, though. This 3D printer, from the pictures, seems to be delivering about 0.2in. That's worse than sand casting. Still worse, some of the errors are in the void direction, undersize. If this thing consistently produced a good solid metal blank, ready for finish machining, it could substitute for having a foundry for small jobs. But it's not even that good.

There are very good, but expensive 3D printers that print excellent metal parts. Check out Space-X's 3D printed rocket engine for the new Dragon spacecraft. Shapeways can now do small steel parts for $10 + $5/cc with reasonable tolerances. 3D printing of metal works now. This welder thing, not so much.