[dom0]

The funny thing about "moving quickly in dynamic languages" is that it doesn't last. Refactoring code in a dynamic language gets difficult fast and is an entirely hopeless endeavour without a huge test suite (you obviously need tests on every level, because you can't refactor an interface and its test at the same time and still think it's working as intended).

Typed code may be slower and more cumbersome (to some) to write in the first place, but is usually much easier to maintain in my experience.

[lliamander]

I find that anything beyond a very small program is faster to do with sort of manifest typing (with static analysis/type checking).

Now, I think that type inference for local variables can be nice (especially if you have good IDE that allows you to see the inferred type).

I once wrote a 600-700 line application in PowerShell. I found myself adding a few type annotations, and I expect that a program any bigger than that (especially if more than one person started working on it) would benefit from a policy of always adding type annotations.