heard all the hype about CK headsets, took the plunge and got them for both bikes - a DJ bike with 100mm forks and a DH bike with 200mm dual crown forks
within 1 month both CK headsets were causing problems I'd never had before with FSA, Cane Creek, etc.
headsets constantly working loose, causing creaking / clicking noises and starting to chew a nice groove in both my fork steerers where the top cap 'o ring' sat.
the lower bearing on the DJ bike actually failed (seized), and Evolution refused to warranty it claiming abuse and just sent me a bill for a new bearing which I refused to pay and returned.
the steerer tube on my DH bike was becoming compromised by the other CK headset, in Whistler the Marzocchi technician who looked at my forks before fitting a new steerer (free of charge, bless 'em) and a FSA Pig Pro headset I'd bought and he said "we've seen this many times with CK headsets"
my riding buddy also with a CK headset on his Marzocchi 66 fork had exactly the same problem, and the Marzocchi people in Whistler also replaced his steerer, we bought them some beers for their troubles!
for riders who keep their wheels on the ground I guess a CK is worth the money?
for riders getting airbourne, I'd steer well clear (to clarify though my experiences were with the older "o-ring" top cap CK design)
never had any issues with my replacement headset which were FSA Pig Pro and Race Face Diablous