I tested it out with some fairly dependency-heavy node JS projects and it worked great (albeit with a human-noticeable perf difference vs node). R projects suffer the usual R-on-JVM issues, see eg https://github.com/oracle/fastr#status-and-limitations . I could, however, use ggplot2 and dplyr, which I don't recall working the last time I tried R-on-JVM. So that's awesome.

Being able to reasonably use R stuff from clojure (and other languages better for general purpose programming) is my data science dream. Though I can't say I'm sad with my current unix-y solutions.

You can check libraries here: http://www.graalvm.org/docs/reference-manual/compatibility/

We don't test all of them but many.

We have considered .NET support but we are not actively working on it right now. But GraalVM is an open platform. Everyone can develop a language for it: http://www.graalvm.org/docs/graalvm-as-a-platform/