Re-work is a consequence of change: changing environment, changing understanding, and changing foundations. Re-work accumulates as a result of these changes. The only questions is when and how we handle re-work. Typically, in the old model, re-work is handled by batching it up as long as possible (until everyone is groaning under the strain of accommodating change). This is often seen in large IT projects when the organization changes technologies (e.g. Mainframe to Client-Server to … to …).

Agile pushes teams and organizations to handle re-work in much smaller pieces. This is hard at first! However, by doing it frequently, it makes people good at it… which means that quality and speed improve.