I feel like we are reiterating our discussion :). My point is people already know Scala, not much to learn there, except for the interface in question. Configuration is a new way to do it, a new syntax, a new thing to learn. Also, if the go from simple to complex during evolution of your app they may have to throw away the config at some point, re-do it in Scala and then extend it. Also the configuration mapper is a second thing we have to maintain. A second way to do it needs a good reason. I don't buy the its simpler argument. I don't think so. I did partly buy the multi-stage compilation is more complex with sbt argument, but was not too happy with it.