We visited from out of town. This museum is amazing - far, far better than the children's discovery museum in our hometown. It's huge, clean, and the toys and equipment are in great condition. We spent 2.5 hours there, and maybe saw/played in 1/3 of the place.
It could really benefit from a cafe, however. The tiny snack room wasn't really sufficient. We were very crowded in there, and food options were unhealthy or kind of gross (I'm not going to go anywhere near an egg salad sandwich in a vending machine).
Overall, incredible museum - our San Jose Children's Discovery Museum could learn a thing or two from it!