Braking in GT5

is a joke, unless you turn ABS off. The "ABS" in that game is a complex 4-channel system, that is "analogue", rather than digital (i.e. on / off), such that the wheels never lock up ever, which doesn't happen in real life. This means that the ABS is also a form of stability control, with a constantly variable, adaptive brake bias (Front / Rear and Left / Right).
Turn ABS off, though, and it gets much more fun instantly. The proper brake bias is maintained in the braking zones, and it makes for a much more tweakable line into the corner, though in general I have to brake a lot earlier as a result. It's more fun, in my opinion, especially when you nail that four-wheel-drift across the apex

Cars like the S1 Elise just come alive. I have a load cell on my G25's brake pedal, which helps with braking consistency, though the base sensitivity could obviously use some work, just as with the clutch.
"Heel and Toe" is not that necessary in Prologue, I've noticed - I go back to GPL and I find that I've been allowed to get very sloppy (right foot braking with a 1-way diff is "fun"), however
Rated-M3 noted that downshifts in the braking zones cause a mild rotation of the rear now, which is promising.