No traits yet. A few other things need to be done first. Generics need to be name-able, System F, and core api is a more pressing need right now.
My plan is to tackle traits in a few months, so long as everything goes well. But I want the above stuff done first, so that when I do traits I can start thinking about higher kinded types, trait inference, and the like.
How does one deal with low coupling? For instance, in PHP I would have used interfaces to decouple collaborators.