I guess the tradeoff here is durability, precision and longevity (negatives) over price (positive). The camera bodies are inexpensive compared to traditionally manufactured cameras of these formats, but aren't likely to be as robust or high quality. Then again, just about any camera that you drop will break, especially the larger formats.
The info on that web site would be insufficient for me to make a purchase decision and I'd need to ask the maker about how the film advance works, whether it has friction on the printed parts that would wear, how the fastener inserts are inserted, etc. (I didn't dig that deep on the site.)
My experience with rapid prototyping and 3d printing is that parts that are designed to mainly take up space (a coaster for your drink, a hockey puck) are perfect for it. It's also an almost perfect way to see how a finished product will look and work, if only briefly. But if you have moving components, friction, the need to flex, fasteners, etc you have to be realistic about what the printer can provide.