The sound when idling is awesome, it will definately turn heads.
It gets to be a little loud when you are full throttle *flying* down the road.
Overall the performance gains are definately noticeable. There is much smoother even acceleration, and I get to 45-50 more quickly than before the upgrades. The clutch spring engages much sooner than stock, and is great for getting off the line, and also getting that extra power down when you need it at speed. The gas mileage has definately suffered a little bit, I am estimating 70-75 mpg instead of 90... but honestly... 75 mpg... who cares?

Overall I am super happy with the setup so far! I would give it 4.5 out of 5 stars.
When people get this upgrade keep in mind that your buddy is still a scooter, and not to expect it to turn into a sport bike by adding an exhaust. I think some people are expecting too much when they get the Prima exhaust, and are let down by their over zealous expectations.
Ducati Seattle sold me the package for $208.97 including tax, plus 1.5 hours labor to have it installed.

