Granted, sometimes you don't care: stuff like `true?1:"foo"` is of type int an has value 1, but the compiler will rejected because of a type mismatch in the conditional—but you don't care because the code smell is too big and obvious to ignore.

Sometimes however you do care, if only a little: the value restriction in ML for instance prevent some function from being polymorphic because some side effect might break the type system. This forces you to eta-expand the function definition (no partial application, you need to write the arguments explicitly), which is a bit of a hassle in some cases.