I was told about this place a long time ago and finally went with my son this week. It was awesome! We spent our time in Artville where it's totally kidproof and touchable. It costs an admission fee for kids over 1 so it made sense for us to buy a membership if we planned on coming a few more times. We'll definitely go back!
Update 2011:
We still have a membership here, it's not too busy on the weekdays, which I have off in the summertime. On saturdays it can get kinda crazy - go early if you can. Bring a sweater if you tend to get cold because the A/C is CRANKED.
Watch out for the people who don't pay attention and let their kids go bonkers in Artville. That area is meant for ages 0-4 and occasionally you'll get some bigger kids in there and/or one of those jerkface kids that is a little brat while their parent is in a corner, texting obliviously. you know what i'm talkin' about.
If you're a member, they have early admission days, usually on a thursday...which would be nice if i wasn't working :(. I wish they would do that on a saturday.