We bought our 2004.5 almost 5 years ago, 2nd owner. We don't put a lot of miles on it, but it has been a great vehicle, 154K on the clock now. We intend to keep it a long time. We use it to tow our TT and for various utilitarian duties. It's a Southern AZ truck from birth, so no rust or corrosion. Very little emissions -- a Cat, but apparently was gutted by previous owner, but it still passes emissions!
I do most of my own maintenance. The Cummins rig is pretty easy to work on. I was lucky that the previous owner put a PacBrake on it -- very advisable to get an exhaust brake if you tow in mountains.
If you can find a clean one for a fair price, IMHO, they are a good choice for a tow vehicle.