I voted critical. Far from being sunshine and flowers critical, though - people don't really grasp how cheap the materials for their moderately fancy toys are compared to the markup they're given. It has the potential to provoke a radical shift in what the first world will buy, and at what price. You're not going to see 3D printers being used in things like construction for a long time, but don't underestimate people's desire to get things cheaper and with more convenience. Unfortunately, that means a lot of jobs shifting around, which means instability. I do think this will make things better, though, in the long run - fewer factories in the second world making us plastic baubles means more of their money being funneled into critical infrastructure, and it wouldn't dry up immediately, so they'd at least have the opportunity to adjust.
It also means less money being spent in retail for us - places like the Home Depot have a head start. If raw materials are what we're buying, the average is going to drop somewhere between freight and raw material and retail markup on the finished goods, more for processed materials. That could be bad news for companies that are making things that can't easily be made by printing - they'll have to buy at the same prices, or set up their own extraction, which means things like cars, etc. will temporarily become more expensive. Far off prediction, large-scale printing becomes forced to innovate to make people these things, and all in all we end up wasting a lot of electricity on complicated and inefficient construction methods. Progress!