Before the rewrite did you consider using Go too? I bring this up because you left it out and since it's a statically typed language I'm surprised you guys ignored it given your Scala background.
yes, Go is kind of unbeatable at writing servers and backend systems.
ya i'm switching to node.js from Ruby. CoffeeTemplates is like dust.js and CoffeeShop is sort of like rails. except tremendously faster! :)