How much planning is too much planning?

By most accounts the conversion of Times Square to a pedestrian mall has been a great success. One way to evaluate success is to count the number of occupied seats, and since nearly all of the seats are always occupied it is a great project that achieved the desired goals. Not so, says the New York Times. The writers for the Times really don't like the plastic chairs. They aren't alone, but I think that the utility of having portable and easily replaced furniture is greater than having fancy cement or other permanent benches. Plazas are hard to design well, and are often over-designed in a way that diminishes their usefulness. Times Square seems to work and people seem to like it. How much more planning is there to do?*

*Obviously maintenance and safety costs need to be accounted for, but those seem minimal at this point.