I've got one on my 06 Classic. I like the sound of it. The only downside is a piece o flex pipe used to connect the stock manifold to the slip on. Also, the cover over the transition from manifold to muffler is the stock one which is made for the two pipes , rather than the single. It looks kind of goofy. I have been considering trimming it to fit.
I'm probably going to buy a header at some point so I'll be replacing it. I didn't like the 3 pipe look or sound of the stock system , even with the cat bypass.