I cannot reply to cdoconnor (probably some downvotes), so I'll write here:

That's the whole point: as it's often said "type checking keeps you honest"

I stumbled time and time again upon badly designed libraries... With a static type system, the painfulness will be obvious and felt the first time you'll try to build your code

with dynamic types, the pain might not be felt at all, until a crazy bit of code will be invoked, sometimes at the most unfortunate of times