Most of the collections API is stable, & there may be a fairly simple alternative for the particular unstable feature you wanted to use. On the other hand, you could also download the nightly branch of Rust to be able to use all of the unstable features.

I think the nature of the 1.0 release and the train model is not very easy to communicate: the Rust team hopes to commit strongly to semver, so "stable Rust" is only that which they are comfortable committing to providing backwards compatibility for indefinitely. It's really pretty fine to be on the nightly track if you don't mind occasionally having to change a method call or something when an unstable API you use change.

Not trying to dismiss what you've said - I just think that the strength with which you expressed it ("Rust is still barely usable") was not accurate & that if you ask in the IRC channel or users.rust-lang.org, there is likely a no-or-little-hassle workaround for whatever feature you wanted.