Have run DP tune in my 7.3 F350 for the last 10 years. Absolutely YUGE improvement in throttle response, engine smoothness, transmission functionality. And somewhere on the order of 40% more torque. Almost like driving a totally different vehicle. And for a 7.3L...it's dirt cheap. You ship Jody the computer and he re-flashes it for like $150. My engine mods are minimal: installed a Walker BTM straight thru muffler, and a Tymar-type air filter I got from Napa. I think I have the 80hp Mountain Towing tune.
For the 6.0L, tuning must be done via a handheld programmer, and that costs $450. Still well worth the cost.