I haven't noticed any handling difference with carbon bars (have them on my roadie, mountain bike, and soon the cross bike as well).

Honestly, I buy the carbon road bars because they are the only ones I can find in my size and in the style I like. I'd be buying them in aluminum as well if they made them in aluminum. Since I haven't ridden my (full carbon) road bike with anything other than these carbon bars I can't really say if they soak up any vibration.

My new wheels however, have smoothed the ride out just a hair.

I would think that bar characteristics such as width, drop shape, and reach would have more affect on handling than material.