Just be sure to follow LLTek's instruction step by step to get the alignment of the exhaust correct.  The new exhaust has a diameter of 2.5" which is bit bigger than stock at 2.25".  Pay extra attention to where the exhaust passes underneath the rear differential.  If you can't slide your pinky between the pipe and the differential, you probably have it too close and it WILL bang against the differential.  I had that problem at first, but it turned out to be a slight manufacturing defect in the placement of the exhaust hanger.  It was easily rectified though with some advice over the phone with the LLTek guys.  The other thing you have to watch for is when you go to install the Y pipe.  When the slide the exhaust clamps back on the stock pipe, make sure you don't let them go over the dimple on each pipe.  If you tighten the clamp over them, the clamp will leak slightly.
     There is only one other gotcha I can think of when it comes to installing the clamps; note their orientation before your remove the stock exhaust.   You may have to adjust their orientation when you go to install the new exhaust.   I had to adjust mine to prevent them from banging against the heat shielding above the exhaust.  Everything else in the install is pretty straightforward.
     The only thing I really didn't like though was how the Y pipe and the resonator bolt together.  Due to where the bolt holes were positioned on the flange it made it impossible to use the washers included.  This could have been a manufacturing problem, because it was the weld on the flange that really got in it's way.  

The exhaust is a little bit louder than stock but not too noisy. I would say it is a bit louder than a stock M3 exhaust.  I wanted an exhaust that was more free flowing but not to loud.  I listened to the 2nd generation Brullen exhaust courtesy of Kurt Williams before I purchased this.  The exhaust I received is the 3rd generation which offers a larger resonator and better fit over the 2nd generation.   At idle, it is hardly noticeable as far as noise level.  It quiets down a lot at highway speed as well.  It's at it's noisiest under full acceleration.  I haven't heard the Stebro exhaust, but I understand that is another excellent cat back exhaust for the 2.8 engine.  The Brullen and Stebro both offer lifetime replacement for rust, etc.  The Brullen is fashioned from stainless steel.