My Ram has the Cummins and 5-speed. I've put about 70,000 miles on it, and it's been extremely reliable; no mechanical failures or problems whatsoever. It gets about 20 mpg on the highway, which is amazing for a truck that weighs 6500 lbs. I wouldn't hesitate to recommend this truck to anyone who needs a heavy-duty work truck.
The Cummins diesel is very well- engineered and extremely heavy-duty. It comes with super-tough Dana 60 front and Dana 80 rear axles. The 4- wheel disc brakes and camper package are great, too. The seats and driving position are great for long road trips. Lots of accessories are available, too.
I'd like to see a stiffer track bar design, and a better shifter for the 5- speed. A factory trailer brake controller would be nice, too.