Lowering springs as bad of an idea as they seem?

I was looking for some general maintenence parts for my bike on sportsbikeshop and found a rear lowering spring for my cbr125r jc50. They make them for all sorts of different bikes and say that they improve handling but was wondering what other people thing. I was considering them as the bike is really really tall and soft from factory but not sure if it would make the bike worse. I'm assuming you can also get a kit to lower and stiffen the fork and balance the bike but not sure. Does anyone have any experience with such parts?