I'm not sure that is still the case. I have an OP-Z and lurking forums for that device reveals tons of posts about build / hardware issues. Luckily my secondhand unit only has SOME broken components but it's pretty widely known as an incredibly fragile device with many design flaws
There's plenty of products made with plastic that holds up well, even in the most harsh environments.
They decided to make the OP-Z out of plastic and it didn't hold up well. It's the fault of their poor design, or at least the type of plastic they decided to use, not the materials.
Not saying OP-1 is a bad product, but it is VERY expensive, and one could argue that the aesthetic of the OP-1 is what makes it a good device.
For something like a PC case, there's already a LOT of options in aesthetics, so asking for nearly $200 for a case (that, as pointed out, you have to assemble yourself!) is a bit much to swallow. $200 gets you basically the highest end case in ANY look that you want. Perhaps not this 'unique', but you have a plethora of options.
I agree that their stuff is high quality concept-wise; at the same time their products are not very durable. E.g. OP-1 is prone to failures; knobs break, ports and keys stop working. In case someone likes high quality and durable products, I recommend doing careful research before buying from this brand.
