Why do you think it's awesome? It's just another zealous implementation of some guys unearned and unfounded ideology. You know you can write the same thing with regular JavaScript and cut out the middle-man.
A polyglot is harder to reason about than a single language, due to social concerns. Mostly this is due to the efficiency of singular concern and custodianship as opposed to disjointed languages with their own.
The purpose of Amber is not to create yet another framework, but to take advantage of the beautiful Crystal language capabilities and provide engineers and the Crystal community with an efficient, cohesive, well maintained web framework that embraces the language philosophies, conventions, and guidelines.
These benchmarks show raw throughput though, and not latency distribution. A well functioning GC should not be too bad in either, and the current solution in the GC area is very much stop the world, so I expect the latency tail to be pretty bad even if raw throughput is damned good.
Well, a couple of breaking changes, but...
still amazing!