It's one of the few places in the US/Canada I've wanted to go to but have never actually been... think I'd prefer to go there outside the primary tourist season though... seems like the crowds would be pretty huge, given how famous an attraction it is.
I can only imagine how busy it gets. We walked through an entirely empty room that was just a queue for the elevator down to the base of the falls. And not having to wait to take pictures without other people in them was nice. I didn't mind either that most of the attractions were closed. Staying in Niagara and doing the activities there can get quite expensive. Instead of eating in town, we stopped at nearby St. Catherine's too.