No crowds to really even speak of. It's a great time to go.
The only downside is during slow times you will see more rehabs, less trams and other transportation, and even shutting down half of rides (sometimes creating a wait time).
When ToT becomes a walk on, you can bet they will shut down half of the elevators. I once recall an elevator WAITING for guests to arrive. Shortly after that there was a 15 minute due to shutting down part of the ride.
Often you will see FP machines covered, as there is no need for them.
The only crowds I can really recall is when a sports groups enter at the same time on one ride. But even that does not happen often. It's just that the crowds are so low, when it does happen, you can't help but notice.
Sometimes you may experience such slow times that you will not even have to get off a ride to ride it repeatedly. This has even happened to us on Splash. Another time we were there RnRC CMs were actually outside trying to bring guests in!
Now THOSE are Kodak moments!

The complete opposite of last week!
