[jared314]

> It seems it has lost whatever popularity it once had

Popularity is always a problematic metric for platform evaluation, because the programming community generally has a very short attention span. I would attribute the lack of marketing to the previous license fight, work towards platform stability of version 2.x, and work on the upcoming version 3.0.

> a polygot application framework sounds like the ideal way to use the right tool for the job.

Vert.x is not completely polyglot. It supports many languages, but they all must compile to JVM byte code to work within the platform's event-loop/thread-pool management. So, the Javascript must run on Rhino or Nashorn, the Ruby must run in JRuby, the Python must run in Jython, etc.