Well, I think your Scala concern is somewhat valid, I'd say that anyone who has a lot of programming experience and knows java well can be productive in Scala w

Well, I think your Scala concern is somewhat valid, I'd say that anyone who has a lot of programming experience and knows java well can be productive in Scala with minimal learning. However, it's less likely you could find a junior programmer or beginner to jump right into scala and 'get it'. Keep in mind, if you go with RoR, you'll have no shortage of developers, but if you're project may encounter issues with scaling. Twitter has documented it's switch from ruby to scala for it's back end quite extensively, may be worth looking into.