Interesting experience report. It’s become a “best practice” to recommend that people try out a new language/tool/hairstyle for non-production tasks like testing, but your experience shows that this strategy is not necessarily the best way to try out any and every new language/tool/hairstyle.

At the OSCON Scala Summit, Alex Payne and Coda Hale did a joint session where they discussed their experiences adopting and using Scala for large-scale production applications (Twitter and Yammer, respectively). They specifically rejected this “best practice” of starting with testing and instead recommended that you solve some nasty problem with your new new tool of choice and thereby demonstrate that the new tool is vastly superior to the old tool, etc.

The size of the Scala language and libraries doesn’t make it a great adjunct tool, like many scripting languages. I think it’s fair to say that it should be your primary tool to justify the effort to master it and use it effectively or you probably won’t get a clear benefit from using it. I’ve made that choice on a few projects and don’t regret the decision, despite immature tools, etc.