Experience is always the key to a good estimate, and for Drupal that's doubly so. This is a session for all experience levels to share how they've done on the projects they've tackled, what was harder or easier than expected, how they might do it differently next time. Also up for discussion is whether Drupal is a good candidate for "Agile" development, a process which helps refine estimating skills and can be helpful in avoiding big schedule changes since it focuses on "bite-sized" development.