Once upon a time, people made the same comments about Ruby and Rails: "it's a fringe language", "the tools are immature", "you shouldn't use it because you can't find Ruby coders", etc., etc.

I find it honestly hilarious to hear it suggested that one of the early high-volume Rails shops should stick with "safe" language choices because they won't be able to hire enough developers to work with a new language.

I've read through the sources to Kestrel, and found them quite easy to grok. If anything, most real-world Scala code seems to be essentially very clean Java, with much of the syntactic cruft (redundant type declarations, inner classes, 'public static final' declarations, etc.) removed. Any experienced, effective developer is going to spend far more time getting to know your in-house APIs and coding style than they are the language.