Agree on papercuts and interaction with other features to some degree. Absolutely disagree on runtime cost. The design of async has as minimal a runtime cost as seems theoretically possible, and avoids a lot of the runtime cost of async in other languages. It's really an impressive engineering feat given the constraints and I think there's a real case for it being a "zero-cost" abstraction (i.e. you couldn't implement a faster version by hand).

IME the bad compiler messages tend to come more often from the `async-trait` macro than from anything fundamental to asyc itself. Hoping the stabilization of async-trait helps with that. Backtraces with async are definitely a bit nasty though.

I for sure hope that Rust gets at least the safety aspect right :) I could endure a lot of suffering if I knew that concern to be taken care of.