It isn't a lot of things, but I would argue that its exceptionally (heh) good exception handling model / philosophy (making it good, required, and performant) is more important than memory safety, especially when a lot of performance-oriented / bit-banging Rust code just gets shoved into Unsafe blocks anyway. Even C/C++ can be made memory safe, cf. https://github.com/pizlonator/llvm-project-deluge

What I'm more interested to know is what the runtime performance tradeoff is like now; one really has to assume that it's slower than LLVM-generated code, otherwise that monumental achievement seems to have somehow been eclipsed in very short time, with much shorter compile times to boot.

How confident are you that memory safety (or lack thereof) is a significant variable in how fast a compiler is?

Zig is less memory safe than Rust, but more than C/C++. Neither Zig nor Rust is fundamentally memory safe.