Phrasing the question that way makes it easier for the person to be critical, since the asker is already implying that there are issues (and is less likely to be let down).

My co-worker used to (humorously but effectively) phrase these questions as, "How can we make this even better?"

Solving for those 'challenges' people pose is the key. However, you have to figure out how to prioritize what to solve. Keep the product CORE intact and have a good vision. You cannot change that all the time. Certainly a great post!

Great point. We still have that list to this day and we keep adding to it.

We even structured our whole company around solving problems. We assign major problems to our teams, they come up with a solution, we pick the best one collaboratively, and those turn into tangible projects.