Agree, you need to spend money on good PADS if you already have brembo's for most people, (R32 GTR non brembo calipers are rubbish).
However for me at around 310kw, proper semi-slicks and more corner speed then I should have at times, I am right on the limit of the brakes with a full weight car doing sub 1.10's. I have trouble locking the tyres and the braking is not progressive. Also looking at the very fast guys they all have the kit or have race cars. So I made the decission to order a AP brake kit, at substantially less then $8K. It probably won't speed me up, but might get me more confidence and added saftey.
So in summary, anyone that has GTR brembo's in a full weight car should be fine using good pads up to and below 1.10's, but at that stage you might want to consider how your braking is working. Or you can just buy the AP kit for the look and knowledge it is cool .