Was is most surprising (well, not really), is the apparent immaturity of Scala tooling (Ammonite), and Akka-based projects like Akka-HTTP and Akka-Stream. If you can get into very cryptic issues when using these project, it makes you reconsider the actual value you get from using a functional, type safe and on-paper concurrent language.

Their proxy is one example where Rust will give the same capabilities as Scala and will be more robust, in the future, if it's not already the case today.