They sound badass, look great and I believe they're even the best value for the money (they come with silencers already in, plus an extra means to silence, and a decat pipe). Only problem is the installation, I had a hell of a time aligning them and had to grind down a bracket to make it fit right. If you're going to have them professionally installed, this isn't a factor, but it helps to know your stuff if you're going to do it yourself.
1) The sound is awesome
2) According to a German magazine test of 8 exhausts for the FZ6, they deliver the most power gain at 3.1HP.
3) They look good, some other makes also look good.
Love mine. One screw on each can to slip out the DB killers, so depending on your mood you can make a little noise (music to my ears) or put them in to attract less attention. Install was not too hard, aligning the cans was a little tricky.
I start my bike up at 5:15 am every morning, haven't had any complaints from the neighbours. Can be a bit noisy between 2-3000 revs, but nothing major.