I purchased my GMC 2500HD SLT 4x4 with the 6.0 engine and locking rear differential to haul my new 8.5 foot slide-in camper. I picked the camper up at the factory and proceeded on a 4500 mile test run. Encountering heavy cross winds in the Dakotas and steep passes in the Rockies had little or no effect on the draiveability of the truck or it's performance. The camper weighs 2370 pounds dry and yet the truck responded with little difference than with an empty bed! Mileage on the way to the camper factory in the midwest ran between 14-16,at speed limit empty and 11-14 with the camper loaded.
This is my first GMC truck and so far I'm pretty happy with it. I have to say though I got what I expected from a 3/4 ton truck. Pulls the loaded dump trailer with ease. Fuel economy is rather dismal but it is a full size pick up with a 6.0L V8 so what can you expect. My power steering pump "whines" which the dealer tell's me that its just the way a 2500HD is. That is the one thing that bothers me the most about the truck.
I have owned 7 GMC/Chevy Trucks over the last 25 years. This truck measures up to the others very well. The only real complaint I have about it is the fact that that it is very light in the rear end. I am a disabled veteran and need to be able to move around in the cab quite a bit in order to stay comfortable and find that this truck gives me the freedom to do so very easily. Riding in friends trucks has shown me that I certainly made the correct decision when I chose this vehicle.
I had an '04 2500 HD and liked it enough that I traded it for an '06 equipped the same. The employee discount was the reason for the switch. It does have a stiff ride, but then, it is a HD instead of a softer pulling 1500. I can pull my 3,000 lb steel horse trailer with 2 horses with an average weight of 1,000 lbs each, and I do not know it is behind the truck. No matter what type of terrain or road condition, as long as it isn't ice covered. We havn't had snow or ice so I havn't had a chance to put it to the real test as yet, other than pulling the horse trailer.