My family (brothers, nephews) have owned at least 6 duramax diesel Chevy trucks. Not a single problem with any of them and they are used for construction business, hauling 5th Wheel trailers (13,000 , 14,500 lbs each), and going over the mountains in good and bad weather including snow an freezing conditions.
Without a load they report approximately 20-22 mpg on the highway. Hauling trailer they do better than my gas powered Chev with a much smaller trailer (5,500 lbs).
I've always liked the comfort and interior of the Chev trucks compared to the Ford and Dodge trucks. My buddies that drive Fords love their trucks and the same story with friends/family who drive Chev/GMC trucks. I've heard lots of complaining about the Dodge trucks from friends but they still drive them because they are cheap to buy?
I've always been a Chev/GMC guy, even though I worked for Ford for several years after high school and a stint in the Army. These days in the Ford and Chevy line ups I think you would have a tough time buying a bad truck. Both have really done their homework and put out a top quality product IMHO. Of course, the prices they charge these days represent that additional effort..... I guess that is why I bought a used 2003 Chev a couple months ago....
Bob