I'm using Atom (on a fairly speedy machine, VS Code has some solid plugin support too) with:
* atom-beautify (with rustfmt installed, `cargo install rustfmt`)
* language-rust
* linter + linter-rust (using cargo check, `cargo install cargo-check`)
* you-complete-me (but YCM is not fun to install, so I'd recommend the racer plugin, both require the Rust source cloned and installed somewhere)
Altogether, those plugins give a pretty good Rust experience.
Is this like anywhere even close to the functionality of something like IntelliJ? Doesn't really sound like it. Linting and formatting, and completion does not an IDE make. How much code intelligence and introspection is there?
Not nearly as much as intellij. However the "linting" in this case is really just highlighting for compiler warnings and errors which are quite good in Rust. That said, you can use clippy (https://github.com/Manishearth/rust-clippy) to get some pretty solid static code analysis as a compiler plug in.
Also, I am very closely following the progress of the rust intellij project, it's coming along nicely.
YCM uses racerd (https://github.com/jwilm/racerd) which keeps everything in a daemon process's memory instead of reparsing every time. It's a good bit faster (at least on my machine), but it uses racer under the hood for recommendations.
