In a city known for gambling and adult excess, this is a surprisingly well done natural history museum and you could easily spend two hours looking through the exhibits.
I agree that there is not nearly enough about the local area and history but some of the other exhibits are very nice like the dinosaurs and the newly added Egypt exhibit with many of artifacts in the recreation of Tut's tomb donated from the now-closed Tut exhibit at Luxor.
The price is reasonable and the location is easy to find but you do need a car or will have to take a taxi. It's conveniently located right next to the Old Mormon Fort and across the street from the Children's Museum so you can take a half a day without even going very far.