@larsberg I haven’t talked to anybody else with the same kinds of large-scale integration concerns that Gecko has, no, and I don’t recall anybody making any pointed complaints about integration of cargo/rustc into other build systems. Unfortunately, I think Servo/Gecko are still trailblazing here. @rovar from 12sided mentioned that they are not using cargo at all and just calling rustc directly from makefiles, but their work is small-scale, using Rust to speed up hot spots. The only company I’ve talked to with scale comparable to Servo are doing a greenfield project completely w/in the Cargo ecosystem.
Perhaps @alexcrichton has information I don’t though.