One of the cool things about the MIVV is a removable insert. I modified mine. I think it flows a little better than it did, but doesn't make quite the racket the can does with no insert at all. A can and a jet kit, which I think is a necessity, really wake up that bike.
599s are a ton of fun. It's been detuned some for midrange, but it doesn't feel like it's had the balls cut out of it like a 919. It's reatined some 600 top kick. 8000+ rpm is where the fun really starts. @400 lbs, aprox 90 hp, it's not hard to get the front in the air or a knee on the ground. It's all very controllable. It's a fast bike, but you'd have to do something real stupid to get into trouble on one.
I've seen Sbeau's yellow 599 and his 919. They both looked like brand new, plus, I think he's a real decent guy.