I am reasonably happy with this function.
I have found that if I bring the car to a stop and apply light brake pressure, just enough to halt the vehicle, it does not activate the stop start. However a firm push down on the brake pedal confirms whether it will activate or not.
Sometimes it is a real pain. When you stop at a junction for a couple of seconds and then there is a safe gap, you move your foot from brake to accelerator and realise the engine has stopped.
That slight delay is annoying.
Like most newish features we just get used to it.