I have the Leo Vince Cat Eliminator with the stock exhaust. I intially thought that the bike revved up smoother, and the surging near idle got better.....but that could have been the placebo effect.
The only reason I got it was to make the exhaust a little louder, and throatier, which it did. I think the bike sound so much better without being too loud. That to me, was worth the $275 or thereabout that I paid for it. The fact that that part of the exhaust does not look like a snake that swallowed an ostrich egg is just icing on the cake.