Changing sprockets is like lowering the final drive in your car. You sacrifice a little potential top speed for quicker acceleration. It's probably the best performance mod for the money.
The most popular mod is to replace the front sprocket with a 14T unit instead of he stock 15T model. This increases the RPM at a given speed so you have more HP at a given speed. The engine feels punchier and more responsive.
It also make slow speed cruising in "stop & go" traffic easier since the engine is turning a slightly higher RPM at the lower speed, you don't have the stuttering and stalling you do if the engine is trying to maintain 600rpm instead of 800-1000rpm so there's less slipping the clutch.
Oh, and it makes wheelies easier.
![Grin](http://ducatimonsterforum.org/Smileys/classic/grin.gif)