You missed the second part: "However ...". :) My point was that it is the planning step that is extremely difficult, not the estimating one. With most real-wor

You missed the second part: "However ...". :) My point was that it is the planning step that is extremely difficult, not the estimating one. With most real-world projects the project plan must follow changing requirements (based on external input or on things you have learned during development). It is extremely unlikely that the original plan will (or should) be followed to the end.