I've heard that overall because of the way these work the results will not come out looking/feeling like LEGO pieces. This is direct result of the method's these use to grow a piece, they deposit material layer by layer thus leaving ridges inbetween layers. Since most LEGO piece are injection molded under pressure to achieve the smoothness on the resulting surface this is a fundamental difference in the results. I'm not saying it cannot work but I doubt you'd ever achieve results approaching the quality that LEGO's production pieces end up with. If i understand the history of these types of machines correctly they were originally developed to make prototype parts some they could be test fitted/measured in place etc before finalized production method's were set. My brother belongs to a Maker group that has amongst their various machines one of these and within it's limits it works from what he has told me when I asked about it. If i ever got the desire to go play with the machines they have I'd be more inclined to machine a few replica parts from metal on one of the CnC machines they've built than try and print new designs but that's me
Build? I merely Acquire atm.