What have been your experiences with the different methods of data gathering for needs assessment? Have you ever done a gap analysis?

Question 1:

What have been some of your experiences with measurement in your organizations? Have some of the errors in measurement been made? Which ones? If your organization has measured the right things right, share that as well.

Question 2:

What have been your experiences with the different methods of data gathering for needs assessment? Have you ever done a gap analysis?