I've been happy with the ecodiesel as a TV. It's very comfortable with the Oliver on the back. The truck actually rides a little better. Mileage wise, we averaged 17.6 mpg up and back on our Yellowstone trip, towing. Without the trailer it averages 27mpg combination city/highway. The greatest benefit to the mileage is the range. We can get over 400 miles on a tank with the trailer attached, which means we only need to fill-up once per day (usually at lunch for us); which far outlasts my bladder. It does great in the mountains. The turbo means you don't loose much power at altitude. Climbing over the passes in the Rockies, we could easily hold 50mph without too much down shifting. Coming down was easier. I usually selected 4th or 5th gear which holds the rig to 45 - 50 mph. Rarely had to touch the brakes.
If I have a complaint, it is that it is quick but not fast. What I mean by that is, when passing another vehicle which is traveling fairly fast, it will jump into the passing lane with authority but as you get much over 85 there isn't much more speed availalbe and you can find yourself waiting for the trailer to clear the vehicle you're passing. I think the Hemi version of the truck doesn't have this issue. But I have found that if I need to go 90 to pass someone, do I really need to pass them?