Just put a pair on about a month ago (07' gt).
Very very nice sound, especially in the low RPM and speed conditions. Not too annoying at highway speeds although definitely louder and 'dronier" than the stock.
People do suddenly now look, and I hear comments as I drive slowly (or not so slowly) by "cool car," or whatever. It brings out the "8" in the V8 is what it feels like.
What I like: Killer low-end/RPM deep growl in addition to when you back off the pedal (completely different tone but sounds great). So You don't have to race the engine to have it sound very cool. Step on the gas in 2nd at near stopping speeds (ie, when you realyl should be in 1st) and the grumbly roar as you take off is very addictive. Too addictive.
If you DO step on the throttle from a stop somewhat enthusiastically, I guess the closest I can think of to describe is NASCAR at the green flag. The roar goes from that low grumble to an insane sports car on steriods type of jet engine noise as you near 5 and 6,000 rpm. Driving in 3rd on a 2 lane parkway with a concrete wall to your left or right has never been so audibly fun since i had my motorcycle.
I haven't heard alot of ther other axle backs out there for '07. I have heard alot of "loud" cars out there that make me cringe how bad they sounds. Granted that I haven't also stood outside the car while someone drives by me in it so I can't really say what it sounds to the casual observer.
All I know is that going from the stock, and then that first press on the gas as I pulled away from the curb the first time I was like "holy s...", and I hadn't even hit 3,000 rpm yet.
Took me about 3 days to get the nerve up to stand at a stoplight and then just gun it, and when I did... "whhhhheeeeeeeeeeeeeah...."
Ah man, the best medicine for a stressful day at work.
So anyway... Would highly recommend. However, will say that the guy who installed for me did indicate he had to make a small modification but nothing major. Had to bend one of the brackets just a touch on the car itself. I didn't really inquire further as I have no desired to ever take them off.