What he said. Knockback usually isn't an issue unless you tend to hop curbs(or kerbs, depending on where you picked up the lingo). My driving style and most of the cars I've setup tended to stay off them, but there was that 1 car that unless you were all up in them, you weren't fast.
Either way, it's a good habit at the track to start using(not just for knockback, but feeling for brake fade as well) of tapping the pedal for pressure before you get to the big brake zones.
I've had a few close calls over the years coming down into T5 and T12 at Road America at 130+mph with a soft pedal... let me tell you, pucker happens... and you learn a new respect for proper pads, fluid, and prep to cars... But when you get it right, and are hanging with prepped C5Z06's in a rust bucket 98 neon...