I just bought this yesterday. I do a lot of towing. I have a 28' gooseneck trailer with a complete mobile shop that I use for doing on-site equipment repair for contractors, ranches, nurseries, cemeteries, golf facilities, etc. I used to have a 2001 GMC Sierra K3500 with the 8.1 and Allison.
I thought the 450 platform would be more suited to my needs. I'm guessing that my trailer weighs at least 16K, probably more. My new truck has 41,000 miles on it and was previously leased. The Oasis report was clean, with no recent warranty work done, it appears clean and reasonably cared for.
What should I be aware of, look out for, over maintain, etc.? Keep in mind that I'm in California, so doing a DPF delete is out of the question, we have to pass a visual inspection for a smog certificate. I did get a 3 yr/36K bumper-to-bumper warranty with it. I typically put 20,000 miles or more a year on a truck and most of it will be towing.
The thumbnail is my trailer and GMC.