Took delivery on May 25th of a 2021 GMC Sierra SLE 3500HD with the 6.6 gas motor that was ordered 12/31/20. We've got 750 miles so far on it and can't find a thing not to like. It's the quietest truck I've ever been in, as in no rattles and really quiet on the highway. It's way more truck than we need for the trailer we have right now but I'm guessing after some longer trips this year and next a bigger trailer of some sort is in the future. We didn't get a bunch of the tech stuff like cameras and lane change alarms and emergency braking, tried to keep the options limited to keep the complexity and cost down. The reason we went with the 3500 was for some reason with the 2 packages we got it only added $400 to jump to the 3500 not the usual $1200 so why not? I was concerned about the ride and did a lot of checking and found that the ride unloaded is the same as a 2500. I haven't driven a 2500 and 3500 back to back but it rides better than the 07 Sierra 2500HD Duramax we had. This is a tall truck, steps or boards are pretty much necessary and this is the only thing I'd change, stock trucks don't need to be this high. I'm 6'1" and can't reach the catch loop under the hood when it's up to close it. It's like a 1500 with a 3-4" lift. No MPG report, mostly driving it locally to get some easy miles on but a 150 mile round trip to Seligman on Rte 66 for lunch indicated 17.7 so not terrible. We did pull the trailer to the CAT scales yesterday and it pulled the trailer effortlessly.