Scala does take more work to learn than Java, but I never choose Java over Scala for a new project. Scala is just so much more modern and expressive.
You can write perfectly readable Scala. It just takes some taste and common sense, or alternatively follow guidelines such as: http://twitter.github.io/effectivescala/
We've found IntellJ + Scala to be an excellent combo for our purposes.
I've been using Sublime as my Scala "IDE" for a while now - what it loses in certain 'critical' IDE features like code completion and variable extraction it gains in speed, ease of use and lack of bloat.
I agree that as far as real IDEs go, IntelliJ is the best - but that's not saying much. The rest are pretty awful. They all do many things poorly, whereas Sublime does a few things very well.
You can write perfectly readable Scala. It just takes some taste and common sense, or alternatively follow guidelines such as: http://twitter.github.io/effectivescala/
We've found IntellJ + Scala to be an excellent combo for our purposes.