It's funny my boss was thinking of trying Scala, but the more he learned about it the more he became disillusioned.
I remember reading somewhere that although you might decide to limit use of Scala language facilities (as there are too many of them), you'll still have to deal with them when trying to understand how libraries work (for debugging purposes for example).
It's not only core libraries, all the available libraries that your project depends upon will one day or the other have to be debugged. I mean I had to debug Hibernate and it was a pain, I can't imagine debugging something written with advanced Scala features that I'm not very confident with.
I remember reading somewhere that although you might decide to limit use of Scala language facilities (as there are too many of them), you'll still have to deal with them when trying to understand how libraries work (for debugging purposes for example).