Comment by steveklabnik

Not all of inline asm is stable yet. The OS I work on at work still has to stay on nightly due to the bits that weren’t (and naked fns, which are apparently also on their way to stable in the nearish future.)

That said those are the only nightly features we use, staying on stable when you can is good, and many projects will be able to go to stable due to this, which is awesome. Been waiting on this for years.