Benjamin C. Pierce's presentation slides (in PDF) for his talk on Types Considered Harmful. The talk starts out discussing some of the general advantages and disadvantages of static typing. But the aim of the talk centers on the problems of building a type checker for the Boomerang Programming Languague (an offshoot of harmony).

Boomerang language design as an example of the need for very precise types some of the technical problems they raise

Contracts as an attractive way of addressing some of these issues

Pierce's work is currently centered on creating a PL for Bidirectional Programming. A work in progress but it's interesting to see the thought process behind language design in real-time.