I have used Jco quite a bit (and contributed a few times) to build out simple utilities binding Rust code to JS [1][2]. I think it is great and the Component Model is the most exciting step towards real useful polyglot libraries I have seen in years. I wish it were better publicized, but I understand keeping things lowkey until it is more fleshed out (the async and stream support coming in Preview 3 are the real missing pieces for my usecases).
[1] https://github.com/awslabs/aws-wasm-checksums [2] https://github.com/landonxjames/aws-sdk-wasi-example