The PC effectively increase the ratio at which the pedal and throttle body open together. In many newer cars that are drive by wire, pushing the pedal to the floor doesn't always equate to the throttle body opening 100%. Or 30% pedal to 30% throttle body for that matter. So the PC makes the pedal feel more responsive. Many people install the PC and love it and are completely happy with it.
My .02.... Does it change the way the truck drives, absolutely. Does it change it in the best way, not in my opinion. IMO even when you put the PC on to the truck, you still have to deal with the terrible shift logic in the Tacoma transmission control unit. Which is by far the worst part of the Tacoma drive experience. So, tuning is what you need. I have been running OVTune on my truck for about 2 years and it changes the truck dramatically because it not only modifies the signal from pedal to throttle body, but it also remaps the engine and transmission entirely.