If I had to take a guess, this is a test market to see if a more street performance oriented truck would sell. It's certainly not a lightning, but they gave it a good engine and made it a bit more oriented to that street performance category. If it sells well, perhaps it could be the beginning of a new lightning program.
As they sit, I don't think they did enough with the truck to justify it's price. I would have liked to see more done in the suspension and brakes and possible something a little more than black wheels and side graphics.
Tremor is definitely lacking in specs to justify the price. But it is only a one year run. Ford announced a while ago that the tremor will not continue into the new body style. I don't know if it is because of a lack of interest in the truck or because they have bigger plans though.