I'm interested to try a pair of Hadley's. I haven't been overly impressed with my King's. My first complaint is that the bearing adjustment needs an american wrench, which is odd because a friend's King hubs (which are a couple years older) use a metric bolt. It's not the biggest deal in the world, but it's a bit of an annoyance having to pull out a different set of wrenches when they need adjustment.
My second complaint is the drag. There's less drag during the warm months, but it's a real PITA not being able to backpedal very far. The hubs drag enough to give me chainsuck. They've got a few hundred hours of riding on them and are properly adjusted. My chainline is good as can be and I've had chainsuck regardless of whether my drivetrain is brand new or worn out. I've ridden other King's that didn't have this problem though, so I don't know what gives.
The super fast engagment is nice and I love the sound they make, but King's prices are through the roof, and from everything I've heard the Hadley's are just as nice.
If you're looking for faster engaging hubs than King or Hadley, check out Industry9. They have 3 degree hubs.
