Just wanted to add that we were skeptical about the Ding! thing (I don't like to download much if I can help it), but the first fare that popped up was the one we wanted, and after booking, we haven't seen anything lower anywhere, so I'm very glad we grabbed it.
We have a family of 5, and it was close to $1000, but I was figuring that at $.35 ish a mile, it would cost us about $700 to drive, and we'd have all the meals on the road too. I know we still have to eat wherever we are, but we tend to spend more on stuff we didn't really want - it was just there - on the road. And we're getting 2 more full days out of our vacation, even after taking away the air travel time.
Between that, and not having 3 kids (one a baby) in the car for 2000 miles, I'm really happy with flying. Plus, we really have to pare down what we bring, and I always love that when we get there.