I really do need to give Rust a try though. I'd been holding back because my impressions of it was the core libraries were still in flux so code that compiled today might fail 2 months down the line. Is this still the case now?
It's true that some cases still use nightly, as some people want to opt into cutting-edge stuff. But it's much much less than it was a while back.
Now, I'm willing to use the bleeding edge, since I'm just just learning the language, but it still just bugs me in that way that code smells always do.
The way how interface{} works there is you actually write your own named structure that is bootstrapped by interface{} rather than dealing with interface{} as a generic type that needs casting. So what you're actually working with is an io.Reader / io.Writer structure but which can be transferred to any domain providing your specific implementation of Reader / Writer supports the same methods (since it's the methods that define the interface you avoid all the horrible hacks than normally trouble interface{}). This means you can transfer data from a gzip archive to a base64 encoder or JSON marshaller to a OS STD* file or network device all as if they were the same logical interface and without having to write a lot of additional layers encoding / decoding the data nor describing the interface. It all works surprisingly painlessly. In fact it's literally the only time when working with interface{} that the process isn't painful.
So it's going nothing to do with fanboyism nor stockholm syndrome, interface{} just behaves quite differently to it's usual behavior and works really well in this specific situation in my personal opinion. If the Go developers left interface{} there instead of using it as a hacky alternative to generics then I doubt there would be the same backlash against it. But sadly they didn't.