How did this exercise help you build empathy with prospective users?
This exercise removes all the barriers and categories which most methods would use, this helps develop empathy with the user. Furthermore when you have no barriers or categories you must listen and breakdown every word which they say and understand where the root of what they are saying (placing yourself in their shoes per say). Only after you have empathized with the user then you categorize the main thoughts, feelings and points brought from the research .
How did the clustering of information help you to understand user needs?
With the bottom up approach you can better divide and sub divide the causes as you do not try to fit the user or the users actions into a preformed chart or list. If one was using a preformed list (top down approach) you there for do not fully understand the needs of the user rather you categorize them. When you move one list into a sub-division of the list or create a new list you can further clarify their needs and in more detail, similarly when you combine two lists together you remove clutter and remove distractions from the real needs described.
What was difficult or challenging with the technique? How would you do it better next time?
The technique is quite a messy technique even though it has a strong structure. It is great that you can consume yourself in the problems at hand but it is difficult to properly cluster the groups together and make sense of the mess. Quite in contrast to what was just said after completing the process that the mess is not the problem but the lack of mess is the problem. The more mess creates more concise clusters and more links between the clusters thus better understanding of the problems at hand.