Smart should've jumped ship the year before last, but wasn't ready or the right offer never came along. He's kind of in a catch 22 position. Saban is still viewed as the mastermind behind the defense with Smart there beside him, but when the defense isn't as good as it is typically (this past season) Smart is the guy held accountable. He's got this year to redeem himself or his stock will fall even more.
As for him as our HC, I'm in favor or young coaches if you're going to take a gamble on an unproven one. In theory they should have the extra fire from youth to give it more than someone who's older and more established. They also don't tend to be as set in their ways. Toss in the less of an age factor for recruiting, you've hit the lottery providing they come with good knowledge and are willing to learn from their mistakes.
We could do far worse, but with another good season he'll be out of our pay range. Big bonus points for learning under one of college football's best coaches, arguably the best one.