I don't like the way they start off with saying that plastic is not a good material to use in headphones, as it stores energy, and creates a muddy sound. Two screens over it talks about the the special fiber filled polymer used as the baffle between the driver and the ears. Last time I checked polymer meant plastic... I also suspect that the special coating for the driver is probably some sort of polymer based film.
Still, I won't own a Grado until my HF2 arrives, so I won't attempt to comment on sound changes.
I just don't like expensive upgrades in which clear contradictions exist in the description and justiication of the mods.