Take all the above comments for opinions, not fact-- and this certainly applies to me. What I can offer, though, is my experience.
I have a CAAD3 Cannondale frame that can be a little, errr, jarring on less than ideal roads. I had an aluminum seat post on it a couple of years ago and picked up a carbon Easton seatpost on eBay for really cheap. I could immediately notice the difference. Some of that, sure, was a placebo effect. But I also think some of it is due to your frame material/design as well as how much "feedback" you're getting from your current seatpost. In my example, I also had a beefy aluminum seatpost that was passing along a lot more vibration/shocks than a lightweight (and arguably less rigid) one probably would have. Combine that post with a really stiff frame and you have a lot of room for improvement. I've been on the Easton post for probably 2+ yrs and it's still going strong. When I decide to replace I'm getting another carbon post.
I recently got Easton carbon bars too. I had lightweight aluminum ones on before and I like the carbon a lot better, primarily because they are much stiffer. I was careful installing them and don't have any reason to expect that they are more suspectible to failure than lightweight aluminum ones.
I would just suggest thinking about what you currently have and whether the potential (marginal) improvements make carbon worth it. Most would say "no" and that's probably right for them. I've been happy with my carbon so far and as long as I perceive it worth the extra cash, probably will continue to use it. As usual, this is highly subjective.
