I have the BMW PE. Only time I hate it (And this is only because my procede requires a placeholder code, so the flapper is permanently open) is on cold start up, when it's enriching the mixture and the engine sits at 1100 rpm. it sounds HORRIBLE then. I also have resonated dp's with no cats.
Otherwise, the other 99% of the time it sounds AWESOME and isn't too loud for my liking. It gurgles, it spits, and rumbles. It sounds just so damn good. It makes the car sound 5 times meaner than it actually is.
At normal idle, and even cruising it's not really noticeable, and I usually roll my window down when I'm gonna be playing the WOT game.
I will never, ever be changing out the axleback section of my exhaust. Nothing will sound better.
2016 e63 amg s wagon matte white
2012 bmw m5 JB4+BCM