There's no doubt there are some nicely modified new diesels out there returning great fuel mileage. However, that's after the owner spends thousands of dollars and throws away the factory powertrain warranty as well. With the cost of diesel powertrain equipment I personally wasn't willing to do that and take the gamble. Others are and that's cool.
Additionally, the above truck is what a $55,000 truck after it's all said and done? We're obviously comparing apple to oranges here. I spent $20,000 less on my 4Runner - that will easily pay for the fuel mileage difference - haha.
Here's some more perspective, let's compare the effect of fuel mileage and cost of ownership over 100,000 miles (more than many will keep their 4runner for, less than some). In 100,000 miles, at 18.5mpg and at $3.00/gallon gas, you'll spend $16,200 on fuel. What reasonable mpg would make us happy? 21mpg? Take that over 100,000 miles at $3.00/gallon and you spend $14,200. That's only a difference of about $2,000 over 100,000 miles and 7, 8, 9 years?
I present that not arguing one way or another but again to provide some perspective. A couple mpg's here and there really doesn't amount to a LOT of $$$ over the years.
(Interesting side note: diesel is now $0.90 more / gallon than gas here in OKC. Using the same figures as above but using $3.90/gallon for diesel, that diesel truck would need to get 24mpg over 100,000 miles to cost THE SAME as an 18.5mpg 4runner).