Historic but Disneyesque
Pros:
As far as recent human history in Utah goes, a visit to Temple Square is essential. The guides are friendly, the grounds are serene, and a look at the structures in the square will help give you an idea of the anglo settlement history of Utah. The Assembly Hall is a very beautiful building, even more so than the Temple.
Cons:
Temple Square is privately owned by the LDS and is understandably teeming with Mormons, so be prepared for a very white-washed and uncritical pro-Mormon experience. The two "tour guides" had very little to say about the history behind Temple Square, and a lot to say about their religion, their scriptures, etc. I would generally recommend that non-Mormon visitors skip the guided tour and explore the place on their own. Also, to get a glimpse of some really bad religious kitsch, go to the top floor of the North Visitors Center. There is a replica statue of Jesus surrounded by murals of "the universe." The guides will even play a recorded "message" from Jesus for you. This is religious Disney at its best.