Experience/Opinion of 6.4L Powerstroke

I have a 2009 6.4 that I bought new. Three years ago I did the dpf delete with a tune and my mileage went up almost 25%. The diesel tech at my Ford dealer actually recommended I do the delete/tune to improve fuel mileage and towing performance. The cost of the work was recovered in less than two years in fuel savings. I have no regrets doing the work, but I would add it's not for everybody as there are downsides. There are more and more jurisdictions that are strictly enforcing EPA laws which will make these modifications prohibitive. Unless you know you are keeping the truck a long time, hold off on the mods until you do (selling a "tuned" truck can be very difficult). Do some research on the tuning sites, Spartan, Bullydog, H&S etc and learn from users.
I baby my truck. Never abuse it and regularly maintain it. The 6.4 has never given me any issues and has performed flawlessly for me.
Best of luck.