It does help in some sense, but not always. I found that, if i wrote out test cases like i am preparing a test scenario document for someone in plain English it works. If i have to open vim and write test cases, i seem to the hack mode and write out the most trivial cases, causing painfully slow development. Test Document + thinking/visualization works better for me.
I've found this as well. Just blindly writing test cases doesn't work so well unless you've already understood the higher level operation of what you're trying to build, and obviously does tend to slow down development.
