The bad part of the summer is the unbearable heat. I freaking hate it. Weeks on end of high 90's to 100+. But like the others have said, you're only minutes from the mountains with their lakes and hiking/biking trails and only a couple hours from really great "roughing it" type camping.
St george heat is too much for me though
What do you do (or want to do) professionally? Coming from Jersey, you're probably going to find SLC a quiet and quaint little town. It feels like a small town, even though it's spread out over 10+ miles.
If you're heading west, you're probably better off making all the way to California, unless outdoors stuff like skiing, hiking, biking, etc. are your thing.
And as many people said, the outdoor activities in the spring/summer/fall are fabulous.