I have 2 bows with carbon in the limbs, an ACS-CX and a R/D longbow built by Lynn Harrelson. I've been shooting the Harrelson bow since 2002 and it has shot thousands of arrows. It is actionboo and carbon 52# @ 28" and shoots a 475 gr arrow around 185 fps. I shot a 52# ACS-CX for a little over a year and recently traded it for a 41# CX. I've shot it quite a bit the last month. I haven't chronographed the 41# CX with my current arrow setup, but it is very impressive with a 455 gr arrow.
Interesting to me, I had a well known bowyer who is a sponsor here told me that he felt the carbon made a bow more consistent in how it shot more than just adding speed. There are some good bowyers on here and some very knowlegeable shooters as well, who I'm sure will give you better insight on carbon limb bows.
I really had not thought about it until now, but two of my three favorite and best shooting bows have carbon in the limbs.