My brother is reading Walter Isaacson's wonderful biography "Steve Jobs" [link to Amazon] right now and he came across the passage that alludes to T.S. Eliot's "The Hollow Men" (p98):
There falls a shadow as T.S. Eliot noted, between the conception and the creation. In the annals of innovation, new ideas are only part of the equation. Execution is just as important.
Between the idea And the reality Between the motion And the act Falls...