My experience of diesels is with my business. I have found that diesel is worth it in vehicles over 5 tons and not worth it in vehicles under. This is, however, from a strictly financial point of view. The real problem diesels have now is the cost of cleaning up their emissions vs the efficiency gains of gasoline engines in recent years.
The real problem these "trucks" have us their enormous size. If the car makers really wanted to reduce fuel consumption, it would make more sense to reduce 500 kg off the curb weight of these behemoths than to develop and expensive diesel engine option, that most probably never achieve pay back in the time the typical owner had the vehicle. We see the same dilemma in the diesel versions that the makers have out now, the $7000 or so extra for the diesel will never be recovered in fuel savings.
I would wager that the next generation of the F-150 will be slimmed down quite a bit. On another note, my organisation has been using Ford trucks for our light duty stuff for many years and they are a good product. We will probably buy one or two next year and we will go for the base V-6, which will have more than enough power for the duties these trucks will perform. But I use these vehicles as trucks, not a huge car. The load capacity, bed length and running costs are the most important factors for me.