As I understand it (this was before my time), early threadless headsets were often of so-so quality, with the exception of the Chris King. Time has passed, headset manufacturing is considerably more advanced and a $20 Cane Creek will last you a lifetime, but the Chris King endures.

They also offer, as I understand it, an unconditional lifetime warranty, like Phil Wood hubs, you would have to replace several headsets to justify the cost.