I've not come across the article before. The section on coupling tests to implementation I guess is the most pertinent part (http://martinfowler.com/articles/mocksArentStubs.html#Coupli...).

> Coupling to the implementation also interferes with refactoring, since implementation changes are much more likely to break tests than with classic testing.

Fowler acknowledges two different styles of tests - state/behaviour also can be termed as classic/mockist. He doesn't really advocate one over the other. I do mock when I have to, but only when there is no other way to setup my test. It is certainly not the default. I find that taking this approach does not make my tests brittle, and makes them robust enough to handle the majority of refactoring exercises.

Of course YMMV.