To me a playback system does not provide anything useful. Never have i found it insightful watching people write code. In fact, most of the insightful stuff comes not from the code itself, but the design and brainstorming process that went on before even a single line was written.
That information can and should be recorded somewhere. The most natural place (I think) for it to be recorded is along side the code where the insights are applicable. The tool was built to allow developers to create these 'stories'.
