I would also argue that you can get the benefits of a static type system with hardly any cost. Usually when people talk about dynamic vs static typing they imagine something like Ruby or Python vs Java, but there's no reason why you can't have a high-level, expressive language with static types.

All you need is a sophisticated type-system and smart type-inference that works everywhere (not just locally) and you'll be able to be just as productive as with today's popular dynamic languages but get all the benefits of static verification.