They are using steel to minimize friction and increase the durability.
Supposedly they wear very slowly compared to normal controllers.
In an interview a few months back with one of the main guys on the project, he said one of their top priorities outside of adding features was minimizing issues like stick drift. The use of stainless steel parts should help prevent wear as well.
The headphone port already works on PC with Xbox One controllers.
Nice, looks like I'll be getting one once they are back in stock and have some more user impressions. Thanks.