I've been a developer for many years, so most of the time I kind of know where I am going and have a map in my head guiding my development. I like test cases to help me with refactoring, but full TDD seems to slow me down when I try it.

I have found that TDD helps quite a bit when coaching a new developer. It sets up intermediate goals that are not as daunting to get to. Sometimes thinking about a big project can just seem overwhelming to someone that hasn't done it before.