If you a binary driver (full on/full off) then this box buys you nothing.
What you will see is that it gives lift / boost at middle throttle settings.
There is no problem with this other than it is a false feedback to the driver. You will get used to the increased thrust at middle settings and then feel deprived of power/progress at the wider/higher peddle/throttle values.
A possible bad/not so good side effect remapping the throttle is that one can think you are not driving the car hard (e.g. 50-60%) but are in fact at a much higher throttle angle (80-90%)
In the end then it is a driver's personal choice.
Where I would see this device being of real benefit is in mapping out the natural flat spots that occur on every car. i.e. engine poer/torque should ideally be linear to pedal position. 0 to 100% in calibrated increments. Sadly this is not the case in most cars. This device, if programmable could provide the linearity we desire without overplaying the effect.