I've not seen it mentioned here (unless included under generic "safety"), but prevention of data races in concurrent code seems like a big thing for Rust. Most examples of Rust being "safe" compared to C are usually about buffer overflows use-after-free, but elimination of data races to me seems like a huge win in its own right. I'm primarily a Java developer and a lot of the practices I'm learning from Rust apply to how I think about implementations in regular work, such as aliasing and mutability.