GoPro isn't going to give you driveshaft speed, input shaft RPM in a stick car, Gs, or a bunch of other stuff, or be able to pick up glitches that a good logger will.

I've heard guys complain about the cost, until they get it in the car. Then it's worth every penny. How much money you spend running up and down the track trying to figure stuff out?

If the results don't match the theory, change the theory.