Either way, you end up keeping lots of things in your head. With dynamic langs, you do have to think about types and use them conservatively. With languages like Java -- the same. No toolset is going to work well unless the dev is on top of things and good at using the tool well.

I've found that debugging in a dynamic environment is great for managing types in a well architected system. It falls down in a poorly architected one, in ways that static typing would not ave allowed. However, in such systems, "it compiles so it must be correct," programmers just get stuck in deeper snow.