Packet pick up sucks because it's down at the far end of the park and there is no easy way to get there except a can or uber and traffic sucks. Not the end of the world, but try to knock it on Friday to put it behind you.
Like other big city races, your GPS is going to give you crap for feedback the first mile because of poor reception because of the high office towers. So hold back that first mile (I went out under 5:20 when I intended to go out in 5:40, but because you are so jacked up, it felt easy).
Port a potties always suck unless your in an upgraded corral, so go early and consider some Imodium so that you don't have to go often.
It is flat as can be. You go over the Chicago River a few times, but those bridges are more like overpasses. Nothing to note really. The biggest clime is right before the 400m to go mark when you go up the overpass on Roosevelt ("Mt. Roosevelt, it is ironiically called).
If you have spectators watching you, it should be fairly easy for them to see you in 3 or 4 spots if they can even run just a little bit.
How fast it will be will be totally reliant upon the weather. Cool day and the times will be fast.