First off, after researching diesel trucks for over a year, it was clear that the Duramax/Allison power train was the "gold standard". I recently installed a Banks air intake, programmer, and exhaust system ($2500) and the performance is startling. Stock, average fuel economy was 16.2 (70 mph+ freeway); I hope the Banks package increases that up to 2 mpg. I stopped to watch a local, weeknight rodeo event in Paso Robles, CA and there were eventually 40+ trucks with 20-30' trailers, all diesels: 1 Chev, 3 Fords, the rest GMCs.
Far quieter than Ford or Dodge diesels. Heated leather seats. Separate temp control for the passenger.
Electric radiator fan(s). Bigger intercooler. Of all the info stored in the computer, only the engine hours resets when the battery is disconnected (i.e., any kind of service).