Brought my nephews here and it seemed to be good for about 2 hours-worth of diversion for a couple of rambunctious 4 year olds. My biggest grip is their ticketing system. It is kind of a pain to have to buy tickets to all the different parts of the complex...just a personal preference, but I would prefer to just pay a flat rate (like $10) at the door and be done with it.
The Pullman Car exhibit was really cool, so definitely spring the $2 for that if you go.