The major difference with rust is that the core language has strong backwards compatibility guarantees, and the package manager supports installing multiple versions of transitive dependencies so packages can be updated incrementally.

Right. GP was complaint about having a gazillion versions of every dependency sitting around to satisfy various whims.

> Don't many of the big rust libraries still depend on nightly, too?

No, none of them do, or at least none that I’ve ever seen in 4 years of doing rust full-time.