I did it a few months ago on my '12 GT (so the install and result should be the same).
In short ... awesome. Coupled with my Roush axlebacks, it's LOUD with the baffles removed. My son's bedroom overlaps the garage by 1/2 and he says when I start the car it shakes his room.
There is some SLIGHT cabin drone at around 2k - 2.5k that you can only hear with the radio off and the windows up. Weather permitting, I drive windows-down most of the time.
It's an expensive mod ... but I am not sorry I installed it. It's awesome. Shop around - I picked mine up for $699.
Install is mechanically easy - but I did it on a set of race ramps in the garage and it was a claustrophobic nightmare that lasted several hours ... there is just no room to work and that made it suck. Hooking up the new h-pipe to the mid pipes was literally me laying on my stomach, flat, reaching forward facing the rear of the car with my head touching the car and my chin on the floor. My car is lowered and it was that tight. On a lift it would probably have taken < 1 hour and been easy.
Again - with anything other than the stock mufflers, it's going to be loud with the baffles removed. Personally, I don't see spending $700 just to block off the exhaust, so I'll never put the baffles in.