It's interesting how all of the prior 5.9 Cummins owners notice big increases in the 6.7. My 6.0 PowerStroke performance was not too far off my current 6.7 Cummins. My 6.0 could out accelerate 6.7, but the 6.7 has more top end speed than my 6.0. This is even more pronounced because I was used to the PowerStroke winding up to greater RPM's on a hard pull and the multi-speed cooling fan sounding like it was a turbine.
Pulling a 4000' climb with 22k lbs GCW last weekend was uneventful and comfortable (like it should be). The climb is relatively short and steep dropping the 6-speed Aisin into 4th at the steepest section (the 5-speed TorqShift was in 3rd here). I have a 3000' climb with about 1000 lbs more coming up soon before we really load up and head to the tin air of Colorado in July.
Prior to buying my truck, I was considering going back to a gasoline engine due to cost of the diesel option. Although I have never taxed a gasser as much as I have my diesels, I don't think I would have been as happy with the 6.4 Hemi. The exhaust brake was good in the PowerStroke, but the EB in the Cummins is great.