We took a trip to Jacksonville a few months ago for a change of scenery and decided to visit the MoSH there. Our little one is a dinosaur fanatic and it just so happens that they had an animated dinosaur exhibit featured at the time. We spent most of the afternoon in that exhibit alone with the little guy telling us what each dinosaur was, marveling at the fact that they were actually moving, and just enjoying him running around from reptile to reptile.
Our older two children were a little bored but still thought the Planetarium show was semi-interesting (little man loved it of course) and the other exhibits as well. They're just not museum type people I'm thinking. I personally enjoyed the slow pace because I could actually keep up with everyone for once!
The little children's corner where kids can play is cute as well. It has a large water table, "treehouse", train table, and several activities for the smaller kids to play with if parents just want to sit and catch their breat for a minute.
Only downside was that the desk staff is a little anal about getting tickets to the observatory.
Definately worth the visit especially if you have the ASDI Museum Memberships (where you get in over 200 museums countrywide for free).