All these same things were said when Ford Field/Comerica opened 14 years ago.
Those were simply arenas, and boring ones at that. This has an entire different level of potential primarily because it's not just an arena but an entire new inhabitable zone (that people can stay at versus going back to the suburbs to eat/whatever). It also blurs the lines between the arena itself and the surrounding concourse/street area. What if on days where there were no events the arena could actually be occupied? How great would that be. You could buy food/drinks/etc from the surrounding businesses and then sit down in the seating. Mad date potential.