New transmission and exhaust brake are excellent. Fuel economy is horrible. Around town we now get about 13 mpg even after 40,000 miles. Towing a 10k trailer we get about 9 mpg. We've already had two different problems with the emissions system. We understand there's a class action suit brewing on this item for all the 6.7's. A quick search on the internet will bring you up to date on this. We loved the 5.9L (had two of them) as it had great power and we usually got over 20 mpg after 50,000 miles. Overall it was a step in the wrong direction, mainly due to the emissions system, and it's still not fixed on the 2010 models.
Transmission, exhaust brake and good pulling power.
Get rid of the emission system and the headaches it brings and give us back the good mileage. The total package negated the whole benefit of having a diesel.