What you will loose is:
Top speed, and you will have higher rew on motorways.
What you gain:
Rewing faster = stronger on all gears.
In slow trafic you can use higher gear = not that nervous in its behaviour.
Just got mine home from service and change sprocket.
Can only say that i love it.
Twisting the throttle on secon gear (3000 rpm) and the front wanted to rice.
(it did not do it before on that rew)
So if you travel on highway a lot, you might be better off with the normal 15 tooth sprocket.