Keep in mind that this park is pretty efficient and has high capacity rides. It takes a lot of people for there to be much of a line build-up anywhere. Plus, the crowds haven't been very big this summer.
During the moonlight madness event, there tends to be an early crowd and a late crowd that switches out, so the total visitor count for the day is pretty high, but during most of the day the park feels pretty light.
I'd say around 6-8pm is probably peak crowds. If you stay till midnight you'll probably get to marathon Time Traveler in the dark.
The really huge crowds won't start showing up until the pumpkin festival starts. I'm curious to see if our pumpkin event will rival Christmas like it does at DW.