I've had several carbon seatposts, including a FSA K-Lite, or something, right now. I also have an alum FSA, a Thomson Elite and a Trek something. I change the whole saddle seatpost out when I want something different---it's easier to just set the seat height and go than swapping a saddle and adjusting it.

I can state with absolute honesty that I cannot tell any increased comfort with a carbon post over the others.

But then, I'm just an ol' hardass.
The Thudbuster might make a difference.