Where does async stand at this point?
* The Pin trait is stable.
* std::task/std::future, i.e., the ability to use futures is still unstable.
* The async/await syntax is still unstable. And apparently being bikeshedded like mad, from what I've heard.
Occasionally a nightly will break your code (the most recent case being when LocalWaker was renamed), and you might have to wait a few more days after that for the futures-preview crate to catch up.