The kids really enjoy it.
We have just purchased our second year of membership to this children's museum. The kids, now 2 and 5, always really enjoy going, begging to go. Some of the exhibits are rather boring, even for older kids (Okay, I looked at it for 30 seconds, now I'm done) For example, the weather station really doesn't have a lot going on, mostly just a forecast and a few measly weather models, and the space center exhibit also is mostly a walk-through type exhibit.
However, some of the exhibits are cool for all ages (an exhibit on crime science and optical illusions are fascinating), and some are mostly for the kids (a water table and fossil dig regularly occupy my children for a half hour, after which I have to drag them away, but they definitely need more seating for adults!) There is an exhibit on fossils and their excavation with a view of a real fossil lab, a small nature center with live animals, a nice view of the Kansas City railroad and its history, a musical park, a miniature golf course, and an electricity show that is free with a regular admission.
On weekday mornings, it feels like you have the place to yourself. It gets more crowded in the afternoons, but not terrible unless a huge group comes in. Weekends are crowded, but the exhibits can still be enjoyed.
The only science center I can compare this to is the Omniplex in Oklahoma City, which I do think has more real science to it, but the kids and grown-ups will enjoy this. Remember that it closes at 5:30, and is closed completely on Monday. Plan to spend all day, especially if you purchase tickets to the theater. There are a few choices to dine in Union Station, the most kid-friendly and reasonably priced being Harvey House, but if you take the 15-minute SkyWalk to Crown Center, there are a huge number of choices, including Crayola Cafe and Fritz's Railroad Restaurant. On weekends, parking at Crown Center is free, so we always park there and walk so we don't have to pay parking (cheapskates, I know!)