If you are a member of the LDS church, this is obviously a place you want to go to see conference. There really isn't a bad seat in the house (seats roughly 20,000) and it's a lot easier to make yourself pay attention (I am a conference napper) there, which is good. Not to mention that is just a breathtaking building. For LDS people, this place is as close to Mecca as it gets. It's wonderful and I think it's a shame to not take advantage of it at least once if you live in the Salt Lake area.
If you aren't a member of the LDS church or are from out of town, it is still worth a visit. Temple Square is really beautiful and this building is one of the more impressive sights there. The creek that runs through it is cool to follow, the interior decorations are very nicely done, the gardens on the roof are awesome, and the things to see inside make it more than just a place where people sit to listen to church leaders.
I can't think of any cons, but it's not worthy of a five star rating because you can only spend so much time there. Also, I live 11 blocks away from it, so I see it all the time.