I’ve had one instance where it went straight to braking - I took a right turn at low speed onto a neighborhood street and encountered a cyclist in my lane coming quickly and directly towards me, about 20 feet away. The car stopped itself. It was jarring but I wouldn’t say it was an overreaction.
I can only think of 1-2 cases where it’s truly given a false alarm - both at low speed on a city street with thick steam coming from a manhole in front of me, which Subaru says in the manual is a difficult situation. Both times I only got a momentary audible alarm; tap the brakes and it stops.
The reliability of AEB definitely varies by manufacturer, but I’m impressed by it.