One of these days I really want to sit down and read a bunch of the takes on different async approaches by the Rust designers, and ponder the design choices in depth. Until then, I will defer judgement. I will say I prefer green threads as a user, but the common argument is that it is not a zero cost abstraction, and thus not appropriate for Rust, makes sense to me atm. I do wish async would get rid of its rough edges though (lack of async drop, async traits, scoped task, etc.) and at least become a first class citizen.