Expensive. That's the only deterrent for me. Some tests indicate they're among the most efficient chains.

But I'm a cheapskate. I buy KMC and replace 'em maybe once a year. Good 'nuff for my old school steel bikes with mid-range components.

I might pony up for a good Shimano or WIppermann chain for a bike build I'm slowly working on. With a mix of Ultegra and Dura Ace components it'd be worth trying a better chain.