Seconded. I could spend more than an hour just on the multi-story spiral slide and in the grotto surrounding it.
Not to mention the stuff they host -- a children's circus, corner shoelace maker/store, papermaking and glassblowing exhibits. And at night, live music, or the outdoor firepits w/ marshmallows provided. One of the upper floors has been converted into condos. I still dream about living on top of that festival.
My only bad experience there was checking out their petting zoo / aquatic exhibit. Some of those animals seemed just this side of mis-treated.