We LOVE ours! We just finished a 6,000 mile southwest trip with it, over a 40 day period. Several times we pulled the well known difficult passes in the Rockies.
Granted, our trailer is fairly light, but there was not a single time that I felt I was even tapping into the power. Climbing 8% plus grades at less than 2500rpm is quite pleasant. :)
There is nothing that I want that this truck doesn't offer me.
BTW, I averaged 11.5mpg over that 6k miles (12mpg for the last 1,000). My average for my work commute is 19.1mpg over the last 5k miles. Impressive numbers for the power available.