One of my best friends from grad school took off for Boise right after graduation. Granted, it's where his family is from originally, but he's never had a bad thing to say about the place. From what I know, it's definitely good for the outdoors type and it's very family friendly. Contrast that to Houston which absolutely sucks for the outdoors unless you get a good ways out of town. I have to say that it annoys me to have to drive over an hour to find anything that even vaguely resembles a hill.
Also, as one of the other posters noted, the air quality can't possibly be worse than it is in Houston, and I'll add that, whatever sprawl Boise may have or be developing, I can't imagine that's worse either.