My only problem with this type of workflow (and the list workflow also) is that often sibling, parent, and child tasks aren't apparent until you are in the middle of, or complete other tasks. So at most I could get a start on a task list/tree, but it wouldn't come close to reflecting reality until the project is completely done. Also, many sub tasks are easier to just do than to describe, yet they don't group together that well under a general parent task.
Of course if a tool could keep track of changes as the project progresses (along with a change log of reasons for each task add/removal), then it could be a good resource improve your estimation skills.
Of course if a tool could keep track of changes as the project progresses (along with a change log of reasons for each task add/removal), then it could be a good resource improve your estimation skills.