I've had mine for about 6 months now. The main purpose of buying this was to get rid of the off-throttle drone that is so prevalent with the stocker, and that's exactly what it accomplished after I installed it. So after 6 months, the sound inside the cabin is about the same as the day I installed it, maybe just a tish louder, but not much. The off-throttle drone is still almost non-existent, which is what I wanted. The thing has a deep note when you're outside the car, which is nice, but you don't really hear it inside. The stocker was an inferno of drone as compared to the Racing Beat.
Still no leaks. You do have to clean it often to make it look good, though, with all that damn soot that builds up.