There is a bit of vibration reduction, depending on the bars. Back in October, I got a set of Cinelli RAM bars used from ebay fairly cheap (well, $250). It isn't just the vibration damping, these bars are molded to your hand shape. If you're like me and spend most of your time with hands on top of the brake hoods, the RAM bars fit your hands perfectly.
Plus, they're just plain beautiful. That shouldn't make a difference, but it does.