Operationally the Prius has a longer travel on the brake pedal before the hydraulic brakes kick in business as usual.

On that upper part of the initial brake pedal travel, it senses that movement in the brake pedal and progressively uses the main MG to brake the car and recover the kinetic energy.

btw recovering rather than dumping the braking energy accounts for the largest part of a hybrid's fuel economy increase.

Below 7 miles per hour there is no MG braking at all, it's all mechanical.. and even in this mode, I can't feel any difference in how the brakes apply, other than the light mechanical sound you get of the pads rubbing the rotors..

You can't feel the transition (at least I can't on my 2006 Prius) from motor/gen braking to normal hydraulic braking..

Hit the pedal hard and it's hydraulic braking business as usual.

On the 2010, if you are in the MG braking, and hit ice, slick surface, etc. or any rough enough surface where the wheels are off the pavement enough to induce ABS, as you are transitioning from light braking to heavier braking, there is a perceptable lag feel stated to be about 1 second, as it transitions from MG braking to hydraulic braking while the ABS is active.

From what I have read this is a software fix to take the lag out..

I get a bit of that same sensation in the ABS on my 4Runner.. which other people have commented years back on all vehicles with ABS that it takes a longer distance to stop with ABS than without due to that sensation.

Braking comparison tests some years back indicate that is not true, with 1 exception.. If you are stopping in heavy mud, where locked up wheels will pile mud in front of the locked tire, then ABS takes more distance than without. Of course, still lots of debates about this one. If I'm about to slide off a cliff, I think I ummmm, prefer the brakes locked solid..

With regard to brake / throttle tie in, there isn't one at present time.. It's being talked about as another way to fail safe all drive by wire throttle systems, if brakes and throttle are applied at the same time, the ECU kills the input to the throttle..