I have the full Muzzy system with carbon fiber pipe. I'd say it's about 20 lbs lighter than stock, no cat (less heat) and looks and sounds awesome. Louder than stock for sure, but not to the point that it's annoying. I would say very similar noise level as my stock 2000 R1.
Some have complained that this system will touch down during a hard right turn, but I haven't experienced that. As a note, my bike has GP set-up forks and a Penske shock, so that could be the reason. Fit and finish is great on the can and OK on the pipe. I'm very happy with it and I'd buy it again!