Not a GM truck, but a 08 Ram 1500. We haven't had the camper for that long, and I added a rear sway bar and air springs to the rear axle. We did a three day trip up Hwy 101 CA to OR, and we just got back from a 12 day trip (Tahoe-Mono Lake/Bodie-Central NV-Elko/Ruby Mountains-SE Idaho-Central Idaho(Stanley)-Eastern OR-NE CA).
After our first short trip, I decided to upgrade all four disc brakes to ventilated rotors and new "towing" pads, not because we had any brake scares but because the brakes were a little squeaky and were about 3 years old. I bedded in the new pads/rotors per instructions after the install. On our first day of the longer trip, coming down a moderately steep grade that had a lot of slow turns on it, my wife said the brakes were getting mushy. We pulled over about half way down the grade and I tested the brakes in the turn out. Mush City, almost completely dysfunctional. I let the brakes cool down a bit and then let the transmission do most of the braking from then on. We didn't have any other "scares", but it set me up for worrying about the truck being overloaded for the rest of the trip. Our camper is 1400# dry, so with the rest of the stuff on board, we are pretty overloaded for our payload rating. We also drove on some fairly rough National Forest roads without any real issues, but it felt like we were beating up the truck a bit.
With our other truck being an 05 Sierra 1500 and replacement on the horizon, we had always planned to get a 3/4 ton down the road to use for the camper, using the 08 Ram in the mean time. On our trip, we decided to get the 3/4 ton sooner rather than later, just so we don't have to worry about killing the 1/2 ton or having any safety issues on a trip. So we purchased a Ram 2500 to put our minds at ease.
Some considerations:
Not sure how heavy your camper is, but we are running a heavy Hawk with everything but a toilet in it. We also like to go on forest roads and other unpaved areas where 4x may be needed. If you are thinking of getting a 2WD, that tells me you probably spend most of your time on decent roads. Lots of people put these campers on 1/2 tons and that's why we did it, because there are so many people that do it without any reported issues. If you downgrade to a 1/2 ton, you can almost guarantee you will need some suspension upgrades, so figure that into your plans. But if it was me, I would stick with a 3/4 ton just for peace of mind.