Absolutely the best!!!
Not from Pittsburgh. Was there on vacation with my kids. They absolutely LOVED IT. Even my youngest, who is hard to entertain, left the place praising it. If you have kids and are in Pittsburgh, this is a great place to take them. We have been to other city's children's museums and this is one of the best.
There are tons of stuff for them to do. There is also a nice variety. Something for everyone. Even my wife and I were entertained. The price of admission was well worth it considering movies are about $10 for only 1-2 hours. We were there for at least 5 hrs and it didn't even feel like it. The best was there were activities that left you with free "souvenirs". We left with various art creations that the kids made that were really cool.