Well-thought design saves time even in agile projects. Maybe it's a one day activity instead of three months of it and yet it makes a difference. Basically each activity (or whatever we call it) is a micro waterfall.

Example from today: a developer came back from a week of vacation, listened to the stand up meeting this morning and pointed out that we misunderstood the purpose of a table he worked on time ago. Result: a few hours of last week's coding were useless and we spent a couple of hours together at redesigning the activity. The total impact should be of about one day.