Nashorn and Avatar are interesting to me, but not personally as much for the ability to write standalone or server-based JavaScript applications.
I see Node.js being primarily used in two different ways. It is used to write those standalone and server-based JavaScript applications, but it is also used entirely in the building and testing process of web applications, primarily with the Karma, Bower, and Grunt Node modules. I imagine there are other Node modules like that that are primarily used as a tool, not as a component in a custom Node.js application. You might consider this a "niche" application, but I'm primarily interested to see whether Nashorn will be able to make it easier to use Gradle to build web applications and run JavaScript unit tests, without involving Node.js.
