thanks all...good suggestions. I guess my curiosity was more about the "clearing your mind" phenomenon. I'm using the lists well, but they are not necessarily taking things off my mind. In some cases, feeling more confident about having them planned for later kind of frees up creative thinking about them when I'm not trying to think about them, if that makes any sense.
In fact, if the "next action" I've calendarized is to develop the project plan, then all the little notes I've accumulated in the meantime are really helpful. But my mind isn't clear of the thoughts. (And the temptation is great to accelerate the next action while it's inspiring me, which isn't always a good idea if my plate is already full.)
I guess it's just an odd example of how GTD spurs creativity!