I still haven't gone fully TDD. I do find myself using it on many of the little pieces of code I write before I ever try to integrate it into the full app. It is just a lot faster to verify each little piece separately does exactly what you want and then connect all the pieces together, than just manually starting from the beginning of integration and seeing how far it makes it before a bug takes halts the progress. Working this way when you integrate the pieces it is awesome to find that most of the time it works all the way through the first time.