I've just been reading about them from the add here too. There is no extra speed to be gained from the carbon bars / stem but there might be from the ceramic bbs/wheel bearings etc. They're claiming 15% smoother/faster spinning. That's a big difference. I read some others claiming 8% (diff. brand) which is still good.
$250 for a package to do the bearings in all the running gear is a fair amount of $ but if your as fit as your can reasonably gear and have fast / light wheels/tyres it's probably as good a next upgrade as you can do.