I've only put a few hundred miles on my bike and just had a 14t sprocket put on it.
HUGE difference in riding experience! The bike is so much smoother now it's a wonder why they don't come like that stock!
It's still a little twitchy on/off throttle puttering around the city, so I may play with the throttle cam a bit to see what I can do there.
Overall I'm very happy with the swapped out sprocket.