I'm using it for hardware libraries that are mostly I/O bound. We're not C10K, we're barely C10, but it's easier than managing threads manually for me.

Interesting! I use rust mainly for embedded. There's a framework called Embassy that uses Async. Mainly built by one guy who's pretty sharp. I prefer to use interrupts, DMA, timers etc directly instead of Async, but it seems that a large number of Rust programmers consider Async to be fundamental. I wasn't sure if that was just the web devs or what, but here are 2 counter-examples.

This made me laugh, but Im in the same boat haha

At my day job (https://buoyant.io/), we're using it to write a reverse proxy/load balancer --- one of the use-cases where you really, absolutely do need asynchronous concurrency. :)