PP… so they are not worth the money then? ;o)
I've got a CK on my Turner(came with it), FSA XL IIs on my two other mountain bikes. I've not really noticed any difference between them in use, but I have had to replace the bottom bearing in one of the XL IIs, but it was over 4 years old and that bike rarely if ever gets cleaned. But as that headset only cost me £20 in the first place, and a new bearing was only about £10 (from Wiggle, even cheaper from a bearing supplier), I reckon that it'd cost about the same as a CK in about 30 years!
Saying that, I'd probably buy another CK if I had the cash and it was for a bling bike… or maybe a fancy CC… but it would be for the bling factor, and not due to better function.