I installed the Corsa cat-back system on my '08 ACR. I bought it from Jon @ Parts Rack after seeing it at a Corsa vendor display at VOI. The construction quality is top notch (and should be for the price), and they went on well. I did have one issue where the locating pin was moved on the '08s, or perhaps just moved on my car, but I got Corsa engaged and they were very responsive. Corsa recommended re-notching the passenger side exhaust, and from there it went fine. I have a lift in my garage which eased installation, and I did all of it practically myself. Take your time, and it'll go well with no damage or scratches to the car. The biggest pain is lining it all up in the exhaust outlets. If you're a perfectionist like me, you'll put the side sills on a few times until satisifed everything is lined up where you want it and ready to bolt down permanently.
Regarding the exhaust note, it's deeper and louder than stock and has a lot more bark on downshifts. It isn't annoyingly loud, though, and I did think it was going to be louder than it is. I'm happy with the sound, and don't need it any louder. The rolled chrome tips also look a lot better than the stock tips.