I too recently upgraded from a ‘19 GMC Sierra SLT to a ‘23 Chevy Silverado LTZ. Love the improvements they’ve made. I switched because I couldn’t find a GMC with Max Tow Pkg within 250 mile radius. But to your question, my mail slot is tight. No movement in the latch area under the hood. So far, no rear window leak either.
I have a 2019 GMC Sierra purchased in Jan 2020 and just 2 months ago the rear window decided to start leaking. Rear window with slider has been replaced. Still waiting for the dealership to install new carpet in the rear after it sat on their lot for 2 weeks soaking up the rainwater.
Previous to that, the 3rd brake light had to be resealed within the first year.
Aside from those two leaks, I’ve had no issues.
I do use Premium fuel and full synthetic oil. I have just over 30k on the odometer today.
6.2 & 10 speed