from the article: " as a Scala advocate, many developers complain to me that the immature support for Scala in IDEs is a real blocker for introducing the language in their Java environments. I understand the practical issue of meeting this now-typical expectation of Java shops, but I actually don’t really care. I seldom use IDEs anymore. My Scala code is so compact that I use Emacs for it."

sUnless you happen to be doing greenfield development, this is a dealbreaker -- I like using scala, but it has to call / manipulate the enormous api surface from 1.5mm lines of existing java. And for that, I need tool support.