Having used their tools at work in anger for years at this point, there is a lot of gotchas, issues and bugs with their bindings at this point -- not all of which is Rust's fault, but the underlying problems with ESP-IDF itself.
That said, its getting better over time, so I'm keeping a close eye on it (and we keep some experimental projects up to test it every couple of months).
The upside of Nim is that "it's just C" at the end, with all the upsides and downsides that comes with.
I'm very hopeful though!
Edit to add: We started this project quite a while ago, too, which forced our hands. Writing unsafe Rust is a pain, so I didn't want to take the burden on for managing bindings myself at the start. If we were to start again, maybe we'd have made a different choice, but Nim at least eased the pain quite a bit.
[1]: https://github.com/esp-rs
[2]: https://github.com/stm32-rs