I have it and absolutely love it. It is loud, but I've heard louder. As far as performance goes I can't comment on that as it is my first slip on. You will piss people off no matter how loud or quite your bike is. Just make sure you can deal with the noise!
I rode my bike with out a muffler when I hit 600 miles all the way to about 4000 miles. Bike never had any problems or threw any codes but it did lose some torque (very noticeable drop). I would at least wait until you get your first service done but since you mentioned you're already getting a...
Depends how often you use the different products. I wash about once a month and I bought my kit two years ago. The only thing I am running low on is the soap and the quick detailer.
I've put 4,500 miles on my FZ8 without using the clutch for up shifting or down shifting. Haven't had any problems. It's really smooth once you get the hang of it.