I'm going to throw my 2 cents in.
I always paid attention to cross and corner weights, front to rear ratio, how LR heavy, etc. and all, but could never drive the car.
The last time I set-up the car, I took what I learned and knew and applied it, made a few minor adjustments, and the car is better than it has ever been (not counting my electrical issues I'm currently experiencing).
I never scaled it.
Set up is important, but I feel that your ass in the seat can tell you more than your car on scales. If its the perfect combination of cross and ride heights, but you can't drive it, is it really perfect?