Got the exhaust installed yesterday at the dealer. The exhaust is not as loud as expected, though I love the sound. It has a unique suction sound that is quite enjoyable. Do not have details on how it really sounds outside since I just got it on. The best way to explain it is that it is about 25-30% louder than stock and the shifting burble sound between gears is much louder.
Also I do not know if this has been discussed but if you have it in park, rev it and lift throttle, there is a much more aggressive burble and pop sound in the sport and sport + mode, which is really enhanced with the m exhaust .
And here's another random one off youtube: