It looks a lot nicer than the muffler Ford used on the CAI. As far as whine and horsepower increases, minimal if any. I've heard whine in videos, but I've yet to hear it from the driver's seat. However, my hearing is crap, so I probably shouldn't even comment on that aspect.
Noticeable increase in whine, well when you have a Vert' and the top down. It would be embarrassing to all other bolt-ons to say any real gains in Power to the wheels.
Go PMAS if you want power!
I think I will be picking one up as well. One thing no one mentions is how much heat the stock muffler keeps and transfers to the intake air. After all it sits directly above an exhaust manifold. On a car that must run well in the winter by emissions law,the heat is probably welcome but I have yet to see a Shelby driven in the winter,not that there is anything wrong with that.
I put one on my car just to clean up the engine bay. If I had it to do over again, I would probably buy the JLT Induction Kit for a cleaner installation.