The four wheel on the fly is critical for me. The awesome power this engine generates is amazing. The ride quality will rival expensive luxury cars. People ask me all the time if it is really a diesel because it is so quiet. They are also impressed with the acceleration, ride quality, and quietness when they ride with me. I will buy another GMC diesel when this one is worn out...in about 20 years or 350,000 miles.
The leather seats are comfortable and easy to keep up. It makes getting in and out much easier too. I like everything about this truck.
The only things I would change about this vehicle is the fender well size to accept bigger tires without doing a 2" lift. I use a Hypertech programmer to increase performance and mileage that could, and should, be programmed at the factory.