because shapeways AKA 'furryways' is not set up to correctly render complex orientations, a lot of 3D product doesn't turn out very good. particularly in the larger scales. if you get a good one, it can look OK in N. my experience is that TT scale models (just a bit bigger) need a lot of sanding.
also, there are questions as to how their materials cope with a range of temperatures. someone who got an NA in one of the garden model railway scales reported it had started to warp and melt in the australian outdoors. i saw obfuscation from furryways advocates on this and other issues. i call it a warning sign when someone has gone from 'best thing since sliced bread' -land to retreating into semantics, rather than recognising a problem. caveat emptor.
my experience with twelve wagons in TT scale is one had warping issues, in the rather milder english summer. the others were stable, but needed considerable sanding to clean them up. so not a bad hit rate, but furryways is not cheap (30 euro a print) and that is for a model that is going to need a lot of work to be ready. i would not want to use their prints in strong direct sunlight.
there was a traceable arc in everyone jumping on the furryways bandwagon for model trains in the UK, which has largely frittered away as the limits of the material and slovenly attitude of the company to quality control have taken their toll.
there are better 3-D printers out there, but i think the consensus is that it is a technology that is not quite there yet, even with companies who will work with designers and who do care about quality. it will happen, i am sure, but give it a couple of years.
in TT, furryways would be useful for more simple prints where the orientation doesn't need to change a lot. it's a dumb technology, ergo, use it for simple things where it won't be challenged, ie, things like boxcar sides, roofs and ends, for example. but because the designers are not that bright overall, and still in love with the 3-D aspect, it really isn't being used for the low end simple jobs where it might be OK.
things where it is out of sight are an idea. for example, retrofit loco chassis that use existing trucks and motors in a new wheelbase, or underframes in their WSF material might be fine, as the WSF is a rigid material and an underframe doesn't need to look that good. who cares if it is a bit furry.
they also have to get a bit smart with their pricing. a lot of furryways designers have no experience of what people are prepared to pay for low end epoxy resin parts, which is what furryways is equivalent to. so someone was trying to sell a boxcar end in HO for 20 euro. wonder how many sales he got? word to the wise: when you aren't that good, charge a low price.