I've had mine fitted about 5 week now, it's wrapped and painted and it has a nice low growl to it when hot.
It has no flat spot (remember it has no pre cat) and revs quite well.
A downside? it touches the subframe under full bore starts, just taps it so it's like a vibration, I'm getting used to it but I have a spare subframe so I'm going to notch it and powder coat it.
Worth the money I think.