As a new hybrid owner, you will hear lots of new whirrs, bells, and whistles, as the HSD resets itself and shuts down. In fact, your HSD will make a whole bunch of clicks as it shuts itself down about 5 minutes after you power off the car. The whirr that you hear while slowing down is related to the regen braking, as well as the CVT lowering the gear ratio as the speed decreases.