Yes, I have the carbotic button clutch as you can see in the link to my build thread, it has the special solid flywheel and the really heavy pressure plate too! Its damn good to drive on the street as you can nearly drive it like a normal clutch once you get used to it, and its been holding up to 360-390kw for over a year and it has not had an easy life....
Jim will run you through the advantage of sprung and unsprung, from memory the main difference was the transfer of driveline noise etc not so much the harshness... Anyway, pick his brains and tell him i said hi! haha