to answer your orginal question dp is a good company. they stand by their product and it does what it says. I would say its one of the better tuners on the market and driveabilty wise its top notch. smoke output is not all that bad unless your getting stupid with it. smoke from the tailpipe is pretty much like normal calibration unless you slam the throttle from a dead stop or heavy load. you can also switch it back to stock with a push of the button.
I run one and love it. I also drive by my exhuast gauge and can turn it down as my load changes. I do alot of towing and hauling and it has really helped with fuel mileage, power and reponsiveness. on the mild ecomony tune it can hang with a 6.0 all day long.
they can also tailer the tunes to whatever you need. Im very picky on a product like a tuner and wont run just any old crap. I did alot of research before shelling out for one.