The speed limit sign reading tech that displays the most recently posted limit on the nav is pretty nifty. (I'd consider that "driver assistance" even if it doesn't physically control the vehicle.)
I have that on my Navigator, and it's mostly decent. The one on my Audi is better, it recognizes school zones and even recognizes active school zones (if there's a flashing light, the 'school' will flash, too). Also very nice (but is dependent on the signals) is the "green light countdown" where the signal is broadcasting how long until a given direction is turning green.
Oh god, the speed limit sign reading. I was in a rented car (a Ford) and it basically spent the entire trip beeping. I didn’t spend time investigating, as it wasn’t my car, but I hope that can be disabled…
Oh, I actually own a Ford - not sure if that's configurable or different depending on models, but I've never heard a beep related to the sign reads. (Or many beeps in general... the only place I regularly get it to beep is when I'm backing up very close to things.)