I have owned upwards of 43 Ford diesel trucks in F-350 & F-450 configuration for the past 30 years for my landscape company. The best motor was the 7.3 turbo. Although the 6.0 has had problems we never experienced any problems with the head gaskets.
When the twin turbo came out, i test drove one and the mileage was terrible so I ended up buying an Obamalet crewcab single wheel truck that listed for 60K. NICE truck!!!. it got 16.7 mpg all day long around town and 22.9 on the highway. after 2 years i found myself needing a new truck so I tried the Fords again. Since the engine option is now about 8600k over the gas motor and the price of fuel is about he same the numbers do not work. you really have to want a diesel. The Ford gas truck, F-350 got 8.2 on the highway in my test loop

and the diesel got 12.2mpg. Not real encouraging. I went down to the Obamalet dealer and got into a 3500 regular cab with the Duramax and went out for a drive. Pulling away from a light the trans went into second gear whereupon i nailed it and promptly broke the rear tires loose. I drove back to the dealer and bought it. It lives its life plowing snow, has a 2 yard salt spreader mounted on it for 4 months of the year and pulls a 20 Haulmark car trailer when needed and is a daily driver. the mileage is around 15.6 with the spreader in the bed. This truck pulls like a raped ape!!!

I drove the Dodge but could not get a good feeling about them. They were priced WAY below the Ford and the Obamalet. In my opinion, having driven Fords for most of my adult life the new Ford trucks are much cheaper "feeling". They are priced about the same
Now....
about the urea as an exhaust treatment:
The material costs $19.00 per 2.5 gallons and a 5 gallon fillup is supposed to last about 5000 miles according to the dealer. GM and Ford are using this system and Dodge will follow in 2012.
Using biodiesel is fine except it eats up rubber lines. we have had to replace the rubber with plastic lined hoses. No issues with lack of power and the bonus is the exhaust smells like McDonalds french fries.
No one hates the idea of Government Motors more than me but I would buy the Obamlet and never look back.