Based on my own design attempts, I think two things are holding back open source hardware design: (1) assembling and reflowing complex boards with parts in small, modern packages (0402 or 0201, QFN, fine-pitch BGAs) and (2) modern CAD features like length matching, differential-pair and multi routing and impedance matching: all the things you'd need to design a fast, wide DRAM interface, for example. (I know some off these features are available in free packages, but IMHO they're just not there yet.) These would open up the kind of designs that are currently only available to elite designers with Altium, things like the RaspberryPi, BBB or bunnie's Novena.<p>I built my own oven and had reasonable luck with two-sided boards with small packages (e.g. 0402) and large 1mm pitch BGAs, but I haven't been able to consistently reflow QFNs. However, it is expensive, time consuming, not buying in bulk kills you, and for complex boards with expensive parts, yield becomes a significant cost factor. I'll be interested to see what their costs are like. A service like this could be transformational.