One of the major reasons why I went with Scala was the seamless Java interop.

There are 1000s of great and well tested components available. Apache, IBM, Yahoo etc. invested years in these, most of the time it just works.

There might be some libraries with issues, but so far I had only good experience with everything from security (bouncycastle) to PDF processing or geocoding.

I don't agree. I think that interopt should be at a higher level, like services. Putting the ability to integrate code not written for your paradigm is problematic. Pragmatic, but still problematic.

It's a lot like Node.js. Why Javascript? Because it is so self contained that it is impossible to use code that violates the paradigm because its too new. When the designer of Node looked at using straight C or another language, the legacy threat put him off. Same thing here.

> I don't agree. I think that interopt should be at a higher level, like services. Putting the ability to integrate code not written for your paradigm is problematic. Pragmatic, but still problematic.

I think if you look at just about any common example of idiomatic Clojure code you'll find Java interop sprinkled all over the place. People aren't going to reimplement all those libraries in Clojure, Scala, or whatever other JVM lang you're targeting. Seamless interop is a prerequisite. I think most Clojurians feel it yields far more benefit than any problems it might introduce.