Wilfred Springer clearly hasn't seen the refactoring tools in Smalltalk, or he wouldn't have let loose with this:

But I also remembered some conference sessions on dynamicly typed languages that I attended in the past. None of these sessions ever mentioned the fact that refactoring tools can be so much more powerful if the type is known before runtime. Renaming an operation in a large codebase would be practically impossible. Tracing the usage of a class would be equally hard.