I suspect that this is an area where Rust shines in a way I haven't seen described for other functional languages, so I don't know if it's as relevant to people

I suspect that this is an area where Rust shines in a way I haven't seen described for other functional languages, so I don't know if it's as relevant to people working in those other languages, but I haven't really written anything performance sensitive and functionally-styled except in Rust. Anecdotally, I have found a couple of times that I needed to manually implement a beautifully simple map/filter/fold call sequence in Rust because it was in a hot loop and just wasn't performing as well as a dynamic programming version that I wrote in the course of benchmarking. I've also found that plenty of times the functional style beat my hand-rolled code, which is an absolutely fantastic result, but I don't think that the compiler is yet sufficiently intelligent to replace all of my hand-rolled loops :).