Here is my experience with the 6.4 power stroke, I drive one every day for my work truck.
If you are lucky and, you won't know it until you own it, you will get one that doesn't go into the dpf regen every 2-400 miles like mine. It will lay a plume of smoke like a James Bond movie for up to 4 miles long doing 60 MPH. It is quite embarrassing to be in when its doing that. As far as the dealers are concerned that is acceptable and within spec's. Some do it less and lots of them are like mine.
This truck is driven in town and hi way mix, averages 150 miles per day and gets between 13 and 14 mpg tops and has 187k on it now, 2004 model auto trans. They have twin turbos which means double the cost if one or both go bad. Marysville Ford just tried to convince me that my lower turbo was bad and would be happy to replace it for $2700.00 and the upper was about $3400.00 (this was a month ago so I may have them backwards). In Ford's genius design you almost can't replace the turbos without removing the cab from the chassis to access them as well as other repairs on the back of the block.
After having it to Marysville Ford 3 times for a "chirping" noise I gave up on them and took it elsewhere. There, I was finally convinced that the real problem is the lifter(s) contacting the camshaft where no lubrication is getting due to a faulty part and basically it will give out soon. Could be 200 miles and could last several thousand miles, but sooner than later. We're talking a new motor for 16-18k and then, it will come with the genius EPA forced upon us DPF system. I am not badmouthing Ford or the dealer at all, simply stating facts.
I currently also have a personal truck which is a 2007 Dodge 6.7 Cummins and this is my 3rd Cummins, 1998 auto trans, 2001 Manual, 2007 manual. In between the 01 and the 07 I had a 04 auto trans Duramax.
Of all of these trucks I enjoy the creature comforts and ride of the Ford the best. It does not ride like a car and haul loads like a car as the GMC did. It doesn't ride like a tank like the dodges have and do, the Ford is between the two for ride. All of the trucks have been loaded packages with all options except the first 98 Dodge which had everything but leather.
If your going to go with a diesel be prepared to spend twice as much on oil changes and, if you don't use fuel conditioner every tank you will be doing injectors it's just a matter of when. The conditioner isn't cheap either. Don't get me wrong, I love these trucks. But, if your going to dive in you need to be prepared for all of this.
I will run my current personal 2007 Dodge until the truck falls apart around the motor, which with a dodge is probably going to happen. I personally won't buy another diesel with the DPF system on them and will switch to a gas motor when my dodge is not worth fixing any longer.
Long winded opinion but, I hope it helps you be a little more informed.
Best of luck!