[defanor]

> Let me ask a more foundational question then, what is the virtue of a "stable" system?

Not introducing breaking changes too often (so that you have to adjust configuration and custom software relatively infrequently), while applying security patches and other bugfixes, and being well-tested to work together are the first ones I think of. With "breaking changes" including changes to configuration, file formats, command-line interfaces, notable behavior, as well as library interfaces. Well, I think it mostly amounts to "knowing that an existing install isn't going to get borked by an update".

Supporting multiple dependency versions and stability guarantees indeed must help with avoidance of breaking changes in libraries, assuming the latest compiler version (or a dependency restriction: either compatible packages in system repositories or if there was such dependency resolution in Cargo), though probably not so much with fixes (I imagine there is less motivation to maintain stable branches and apply fixes to those then) and with integration testing. Besides, not all software is written in Rust: other packages and ecosystems must be taken into account as well. Likely more varied ecosystems can be handled more smoothly with NixOS or GuixSD, but I am not risking to use them on anything that should be reliable yet (maybe it is the time to look into those again though). But this kind of poor compatibility with stable systems does not seem necessary, especially for a language that is supposedly a safer alternative to C, while C is about as well-integrated into--and compatible with--common (POSIX) systems as it gets. Though then again, above it was noted that our experiences with C differ, but this is how I see it.