There's been no issues with it. As for sound, I got the louder option and it's still only just more noticeable than a stock system. My girlfriend has a Miltek but the normal GTI design and it's a bit louder than that.
If I were you I'd order a BCS exhaust, I reckon if I replace my down pipe and cat, I'll also have them make a full exhaust. Worth a few hours drive, the many cars I've seen with BCS fitted have been stunning craftsmanship.