It's been annoying to me as an end user that so many basic things require nightly. I use nightly as my main toolchain, but enabling unstable features makes a project nightly-only, which is undesired for crates that don't already revolve around the unstable feature.

I most often encounter unstable features when I reach for a basic common-sense utility method and discover that it's not stable. Like just earlier today I would have reached for bool::toggle which not only is unstable, but is also newly added as of like a month ago! but some unstable methods have been sitting around for years.

And now that IntelliJ-Rust is proprietary, I can't even make a feature request anymore for the ability to exclude unstable features from the autocomplete. So they will taunt me forever, perfect little helpers just locked away.