I have a carbon post on my TCR and it does actually make the ride more comfortable. I was sceptical as first but after a year I am convinced it is more comfortable than an aluminium post. Some clown that I ride with put a 4km section of dirt in one of our races recently and the ride was a lot smoother than my other carbon bike with an aluminium post. Carbon is great for the bumps. I don't care how much it cost, that's why I work.
CHEERS.
Mark