Here's a video of Kauli with his new 3 batten KS3 sail.
I was lucky enough to use a 4.3 KS3 for 6-7 sessions.
The sail is incredibly stable in all conditions. It's also very, very powerful and it pretty much disappears when riding a wave down the line.
I personally prefer flatter sails like the Firelight (a bit less power), but I live in Maui and I like to ride waves with a small sail in very light wind conditions, hoping to feel as little power as possible in the sail. In other words, not exactly what most of the wave sailors are looking for when they go sail.
Give them a try if you like a sail that pulls a lot and is light and maneuverable.
Kauli's KS3 Evolution from Hot Sails Maui on Vimeo.