I think TDD is great when you know what the code should do. When I'm writing parsing code or something else very utilitarian I definitely prefer to write the tests first. As a Flex/Flash developer, most of my code is directly for the UI, and often I find that I'm not entirely sure what my code should do right away. I'm becoming a big fan of the Presentation Model pattern, but even with that, I find that it takes exploratory development to determine exactly which component should do what and which logic should go where.  I found it very burdensome to update both the regular code and tests step-by-step . Not being a TDD expert I could easily be doing something or interpreting something incorrectly. Or perhaps I'm just lazy.

I've decided, at least when it comes to UI development, to follow a looser Testable-driven development technique. As I'm fleshing out my component logic, I constantly ask myself, "Is this code testable?" or more generally "How will I know if this works?" This primitive technique gives me the freedom to write exploratory code while helping to reign in potential magic logic. I then write tests once things have settled down, refactoring any logic to make things more testable as necessary. This technique also fits my style of coding where I like to sketch out logic with small tracer bullets.  It definitely takes some discipline to think about the testability of the code, but so far I'm much more comfortable with testable-driven development for UI work.