First off, this is a free museum, so you can't expect the same level of "wow" that you would at a paid museum. That said, their displays are fantastic, enjoyable, and there's a lot of really awesome artifacts. Everything is fairly well explained, and there's just a lot of really interesting stuff.
It does get a bit crowded, and sometimes the displays feel almost braggy about Wisconsin's involvement, but overall it's really cool and very educational!