It never hurts to read criticism and downsides to some technology as an antidote to rosy tainted hype. Here are two not so positive accounts of Scala. This first one is a recurring theme in criticisms of Scala, namely that it’s too complex, cryptic, overly complicated:
Besides the comments addressing specifics of that post, here’s a general response to criticisms of Scala as overly complex by Martin Odersky. The notion of language complexity is a deep subject that I’ve been thinking about lately, so I’ll save discussion for another post.
Moving on, perhaps Scala’s biggest public embarrasment to date is the Yammer fiasco, where a move from Java to Scala was initally promising but eventually proved not to be worth it. The code was moved back to Java. Here’s the original critique:
The story with Yammer has some overlap with the first criticism above; again the issue of complexity is brought up, and in particular how this is a problem since there is a shortage of engineers with Scala experience. But besides more academic considerations of language complexity, what the Yammer story seems to point to is the relative immaturity of Scala as an industrial language. I recall some comments saying that the problems brought up about Scala today are reminiscent of criticism of Java in the 1.3 days, and that these issues are a natural part of a language’s evolution and improvement that will be resolved in time. Typesafe seems to be going down the right path.
But if we accept this interpretation, Scala’s successful evolution is a matter of resources. Does typesafe have the financial muscle to address these issues diligently? Maybe!
 Commenters point out that the collection excercise the writer attempts as evidence of excessive complexity is unnatural, useless, and in fact impossible in any language, but Scala actually comes close