I have just got back from a half-day hike from Berowra to Mt Ku-ring-gai. The 9.5km track took three of us 3 hours 30 minutes to complete. During that time one of my mates got managed to fall into a stream we were crossing, and then attacked by a leach, while the other grazed his knee crossing another stream. However, I managed to survive with no damage.
More details on the track are available on the Wild Walks website.